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PubMed2004

Contribution of aldehyde oxidase, xanthine oxidase, and aldehyde dehydrogenase on the oxidation of aromatic aldehydes.

Aliphatic aldehydes have a high affinity toward aldehyde dehydrogenase activity but are relatively poor substrates of aldehyde oxidase and xanthine oxidase. In addition, the oxidation of xenobiotic-derived aromatic aldehydes by the latter enzymes has not been studied to any great extent. The present investigation compares the relative contribution of aldehyde dehydrogenase, aldehyde oxidase, and xanthine oxidase activities in the oxidation of substituted benzaldehydes in separate preparations. The incubation of vanillin, isovanillin, and protocatechuic aldehyde with either guinea pig liver aldehyde oxidase, bovine milk xanthine oxidase, or guinea pig liver aldehyde dehydrogenase demonstrated that the three aldehyde oxidizing enzymes had a complementary substrate specificity. Incubations were also performed with specific inhibitors of each enzyme (isovanillin for aldehyde oxidase, allopurinol for xanthine oxidase, and disulfiram for aldehyde dehydrogenase) to determine the relative contribution of each enzyme in the oxidation of these aldehydes. Under these conditions, vanillin was rapidly oxidized by aldehyde oxidase, isovanillin was predominantly metabolized by aldehyde dehydrogenase activity, and protocatechuic aldehyde was slowly oxidized, possibly by all three enzymes. Thus, aldehyde oxidase activity may be a significant factor in the oxidation of aromatic aldehydes generated from amines and alkyl benzenes during drug metabolism. In addition, this enzyme may also have a role in the catabolism of biogenic amines such as dopamine and noradrenaline where 3-methoxyphenylacetic acids are major metabolites.

Aldehyde Dehydrogenase↗
PubMed1994

Mechanism of aldehyde inhibition of Vibrio harveyi luciferase. Identification of two aldehyde sites and relationship between aldehyde and flavin binding.

Vibrio harveyi luciferase is sensitive to aldehyde substrate inhibition, and two kinetic schemes have been previously postulated to account for such an inhibition. One scheme depicts a sequential binding of 2 aldehyde molecules, yielding an active enzyme-aldehyde binary complex and subsequently an inactive enzyme-(aldehyde)2 ternary complex (Holzman, T. F., and Baldwin, T. O. (1983) Biochemistry 22, 2838-2846). This two-aldehyde model was later withdrawn, and recently, a different scheme was proposed, following which the prior binding of one aldehyde to the native luciferase forms an inactive dead-end complex (Abu-Soud, H. M., Clark, A. C., Francisco, W. A., Baldwin, T. O., and Raushel, F. M. (1993) J. Biol. Chem. 268, 7699-7706). In this work, kinetic and equilibrium studies were carried out to elucidate further the mechanism of aldehyde inhibition. Two, presumably independent, aldehyde-binding sites were detected, with a higher affinity site for the aldehyde substrate and a weaker affinity site for the aldehyde inhibitor. Binding to and dissociation from the inhibitor site by decanal were revealed by chemical relaxation analysis to be slow processes. Furthermore, whereas the binding of the decanal substrate enhances the affinity of the reduced riboflavin 5'-phosphate (FMNH2) site, the binding of decanal to the inhibitor site competes against FMNH2 binding, thus resulting in inhibition of luciferase activity. These findings are not compatible with either of the two earlier schemes mentioned above. A new kinetic model is formulated for the mechanism of aldehyde inhibition. Theoretical kinetic behaviors predicted on the basis of this model are in excellent agreement with experimental observations. A particularly reactive cysteine (residue 106) on the alpha subunit has been previously demonstrated to be at or near an aldehyde site (Fried, A., and Tu, S.-C. (1984) J. Biol. Chem. 259, 10754-10759). Evidence is presented to indicate that this residue is at or near the aldehyde inhibitor site. Relative locations of this residue and binding sites for FMNH2, the aldehyde substrate, and the aldehyde inhibitor are proposed.

Aldehydes↗
PubMed1991

Structural features of stomach aldehyde dehydrogenase distinguish dimeric aldehyde dehydrogenase as a 'variable' enzyme. 'Variable' and 'constant' enzymes within the alcohol and aldehyde dehydrogenase families.

Stomach aldehyde dehydrogenase was structurally evaluated by analysis of peptide fragments of the human enzyme and comparisons with corresponding parts from other characterized aldehyde dehydrogenases. The results establish a large part of the structure, confirming that the stomach enzyme is identical to the inducible or tumor-derived dimeric aldehyde dehydrogenase. In addition, species variations between identical sets of different aldehyde and alcohol dehydrogenases reveal that stomach aldehyde dehydrogenase exhibits a fairly rapid rate of evolutionary changes, similar to that for the likewise 'variable' classical alcohol dehydrogenase, sorbitol dehydrogenase, and cytosolic aldehyde dehydrogenase but in contrast to the 'constant' class III alcohol dehydrogenase and mitochondrial aldehyde dehydrogenase. This establishes that rates of divergence in the aldehyde and alcohol dehydrogenases are unrelated to subunit size or quaternary structure, highlights the unique nature of class III alcohol dehydrogenase, and positions the stomach aldehyde dehydrogenase in a group with more ordinary features.

Aldehyde Dehydrogenase↗
PubMed1985

Identification of pig brain aldehyde reductases with the high-Km aldehyde reductase, the low-Km aldehyde reductase and aldose reductase, carbonyl reductase, and succinic semialdehyde reductase.

Four NADPH-dependent aldehyde reductases (ALRs) isolated from pig brain have been characterized with respect to substrate specificity, inhibition by drugs, and immunological criteria. The major enzyme, ALR1, is identical in these respects with the high-Km aldehyde reductase, glucuronate reductase, and tissue-specific, e.g., pig kidney aldehyde reductase. A second enzyme, ALR2, is identical with the low-Km aldehyde reductase and aldose reductase. The third enzyme, ALR3, is carbonyl reductase and has several features in common with prostaglandin-9-ketoreductase and xenobiotic ketoreductase. The fourth enzyme, unlike the other three which are monomeric, is a dimeric succinic semialdehyde reductase. All four of these enzymes are capable of reducing aldehydes derived from the biogenic amines. However, from a consideration of their substrate specificities and the relevant Km and Vmax values, it is likely that it is ALR2 which plays a primary role in biogenic aldehyde metabolism. Both ALR1 and ALR2 may be involved in the reduction of isocorticosteroids. Despite its capacity to reduce ketones, ALR3 is primarily an aldehyde reductase, but clues as to its physiological role in brain cannot be discerned from its substrate specificity. The capacity of succinic semialdehyde reductase to reduce succinic semialdehyde better than any other substrate shows that this reductase is aptly named and suggests that its primary role is the maintenance in brain of physiological levels of gamma-hydroxybutyrate.

Alcohol Oxidoreductases↗
PubMed1983

Pig muscle aldehyde reductase. Identity of pig muscle aldehyde reductase with pig lens aldose reductase and with the low Km aldehyde reductase of pig brain and pig kidney.

A monomeric (Mr = 43,000) NADPH-dependent oxidoreductase with a broad substrate specificity for aliphatic and aromatic aldehydes and aldo sugars has been purified from the skeletal muscle of female and castrated pigs. The properties of this enzyme are consistent with those of aldose reductase (EC 1.1.1.21), and the enzyme is immunologically identical with aldose reductase from pig lens. However, antiserum to pig muscle aldehyde reductase also cross-reacts identically with the low Km aldehyde reductase from pig brain and kidney and the pattern of inhibition of the muscle reductase by anticonvulsant drugs is the same as that obtained for the low Km reductase. These intraspecies results yield the first definitive evidence that pig muscle aldehyde reductase is the same enzyme as aldose reductase and that the latter is identical with the low Km aldehyde reductase, one of two major aldehyde reductases found in mammalian tissues.

Alcohol Oxidoreductases↗
PubMed1996

Distribution of messenger RNAs for aldehyde dehydrogenase 1, aldehyde dehydrogenase 2, and aldehyde dehydrogenase 5 in human tissues.

BACKGROUND: The distribution of aldehyde dehydrogenases in human tissues is incompletely understood, in part because of technical limitations of gel electrophoretic and other enzyme assay methods used previously and because of the instability of the enzymes. Since these enzymes participate in detoxification of endogenous and exogenous compounds, including ethanol, their tissue distribution may be relevant to the toxicology of a number of substances and to the medical consequences of alcoholism. METHODS: The abundance of mRNA for aldehyde dehydrogenase 1 (ALDH1), aldehyde dehydrogenase 2 (ALDH2), and aldehyde dehydrogenase 5 (ALDH5) was determined by Northern blotting using poly A+ RNA from 16 adult human tissues and 5 fetal tissues. RESULTS: The highest levels of ALDH1 mRNA were found in liver, kidney, muscle, and pancreas. ALDH2 and ALDH5 were expressed in a larger number of tissues than ALDH1, with highest levels in liver, kidney, muscle, and heart. Fetal heart, brain, liver, lung, and kidney expressed ALDH2 and ALDH5, while ALDH1 was present mainly in fetal liver, kidney, and lung. CONCLUSIONS: The results are in general agreement with the distribution of enzymes studied in a limited number of tissues in the past, with the exception that the ALDH1 activity reported to exist in heart and brain may, in fact, be ALDH5. The only mRNA detected in placenta was that for ALDH5. This study extends the knowledge of the expression of these enzymes to several tissues not previously studied and establishes the tissue distribution of the new enzyme ALDH5.

Adult↗
PubMed1984

Electrophoretic analyses of alcohol dehydrogenase, aldehyde dehydrogenase, aldehyde reductase, aldehyde oxidase and xanthine oxidase from horse tissues.

Cellulose acetate zymograms of alcohol dehydrogenase (ADH), aldehyde dehydrogenase (AHD), aldehyde reductase (AHR), aldehyde oxidase (AOX) and xanthine oxidase (XOX) extracted from horse tissues were examined. Five ADH isozymes were resolved: three corresponded to the previously reported class I ADHs (EE, ES and SS) (Theorell, 1969); a single form of class II ADH (designated ADH-C2) and of class III ADH (designated ADH-B2) were also observed. The latter isozyme was widely distributed in horse tissues whereas the other enzymes were found predominantly in liver. Four AHD isozymes were differentially distributed in subcellular preparations of horse liver: AHD-1 (large granules); AHD-3 (small granules); and AHD-2, AHD-4 (cytoplasm). AHD-1 was more widely distributed among the horse tissues examined. Liver represented the major source of activity for most AHDs. A single additional form of NADPH-dependent AHR activity (identified as hexonate dehydrogenase), other than the ADHs previously described, was observed in horse liver. Single forms of AOX and XOX were observed in horse tissue extracts, with highest activities in liver.

Alcohol Dehydrogenase↗
PubMed2003

Stereochemistry of the allylation and crotylation reactions of alpha-methyl-beta-hydroxy aldehydes with allyl- and crotyltrifluorosilanes. Synthesis of anti,anti-dipropionate stereotriads and stereodivergent pathways for the reactions with 2,3-anti- and 2,3-syn-alpha-methyl-beta-hydroxy aldehydes.

A new method for the stereoselective synthesis of the anti,anti-dipropionate stereotriad via the reaction of alpha-methyl-beta-hydroxy aldehydes with (Z)-crotyltrifluorosilane (24) is described. These reactions were designed to occur through bicyclic transition states (e.g., 31) in which the silane reagent is covalently bound to the beta-hydroxyl group of the aldehyde and the crotyl group is transferred intramolecularly. This methodology was used to synthesize the C(7)-C(16) segment (58) of zincophorin, which contains a synthetically challenging all-anti stereopentad unit. Surprisingly, 2,3-anti- and 2,3-syn-alpha-methyl-beta-hydroxy aldehydes react in a stereodivergent manner with 24: 2,3-anti-beta-hydroxy aldehydes give the targeted anti,anti-dipropionate adducts with high selectivity, but the reactions of 2,3-syn-beta-hydroxy aldehydes are poorly selective. The stereodivergent behavior of 2,3-syn- vs 2,3-anti-alpha-methyl-beta-hydroxy aldehydes is also exhibited in their reactions with the allyl- (68) and (E)-crotyltrifluorosilanes (27). Competition experiments performed with beta-hydroxy aldehydes 37a (anti) and the corresponding p-methoxybenzyl (PMB) ether 48, and between aldehyde 39 (syn) and the PMB ether 90, established that the 2,3-anti-beta-hydroxy aldehydes react predominantly through bicyclic transition states while the 2,3-syn aldehydes react predominantly through conventional Zimmerman-Traxler transition states. NMR studies established that both the 2,3-syn and the 2,3-anti aldehydes form stable, pentavalent silicate intermediates (98 and 100) with PhSiF(3), but chelated structures 99 and 101 could not be detected. The activation energies for the competing bicyclic and conventional Zimmerman-Traxler transition states were calculated by using semiemperical methods (MNDO/d). These calculations indicate that the stereodivergent behavior of the 2,3-syn-beta-hydroxy aldehydes and the 2,3-anti-beta-hydroxy aldehydes is due to differences in nonbonded interactions in the bicyclic transition states. Specifically, nonbonded interactions in the bicyclic transition states for the allylation/crotylation reactions of the 2,3-syn-beta-hydroxy aldehydes permits the traditional Zimmerman-Traxler transition states to be preferentially utilized.

Aldehydes↗
PubMed2004

Metabolism of isovanillin by aldehyde oxidase, xanthine oxidase, aldehyde dehydrogenase and liver slices.

Aromatic aldehydes are good substrates of aldehyde dehydrogenase activity but are relatively poor substrates of aldehyde oxidase and xanthine oxidase. However, the oxidation of xenobiotic-derived aromatic aldehydes by the latter enzymes has not been studied to any great extent. The present investigation compares the relative contribution of aldehyde dehydrogenase, aldehyde oxidase and xanthine oxidase activities in the oxidation of isovanillin in separate preparations and also in freshly prepared and cryopreserved liver slices. The oxidation of isovanillin was also examined in the presence of specific inhibitors of each oxidizing enzyme. Minimal transformation of isovanillin to isovanillic acid was observed in partially purified aldehyde oxidase, which is thought to be due to residual xanthine oxidase activity. Isovanillin was rapidly metabolized to isovanillic acid by high amounts of purified xanthine oxidase, but only low amounts are present in guinea pig liver fraction. Thus the contribution of xanthine oxidase to isovanillin oxidation in guinea pig is very low. In contrast, isovanillin was rapidly catalyzed to isovanillic acid by guinea pig liver aldehyde dehydrogenase activity. The inhibitor studies revealed that isovanillin was predominantly metabolized by aldehyde dehydrogenase activity. The oxidation of xenobiotic-derived aromatic aldehydes with freshly prepared or cryopreserved liver slices has not been previously reported. In freshly prepared liver slices, isovanillin was rapidly converted to isovanillic acid, whereas the conversion was very slow in cryopreserved liver slices due to low aldehyde dehydrogenase activity. The formation of isovanillic acid was not altered by allopurinol, but considerably inhibited by disulfiram. It is therefore concluded that isovanillin is predominantly metabolized by aldehyde dehydrogenase activity, with minimal contribution from either aldehyde oxidase or xanthine oxidase.

Aldehyde Dehydrogenase↗
PubMedDate not supplied

Interactions between aldehyde derivatives and the aldehyde binding site of bacterial luciferase.

The interaction of triazine aldehydes with the aldehyde binding site of bacterial luciferases was investigated using a series of triazine aldehydes with different aldehyde chain length, and substituents on the s-triazine ring. Substrate activity was determined using luciferase from Photobacterium fischeri and Vibrio harveyi in a dithionite-based luciferases assay. The chain length optimum was determined for two triazine aldehyde classes to be C-10 and C-11, respectively. Only the substrate activity of 10-(4-chloro-6-methylthio-s-triazine-2-yl)aminodecanal (5) was as high as n-decanal, the reference aldehyde. All other triazine derivatives reduced light emission, probably by hindered binding of the substrates. The degree of activity reduction correlated with the volume of the triazine ring moiety. The triazine moiety volume of compound 5 was estimated to be 200 x 10(-30) m3. Triazine aldehydes which showed reduced light emission had an estimated volume of 228 x 10(-30) m3 or greater. All triazine aldehydes showed approximately 10-fold lower activities for Vibrio harveyi than for Photobacterium fischeri luciferase. Substrate specificity was the same for both luciferases. A schematic superposition of quinone aldehydes and triazine aldehydes which showed substrate activities equivalent to n-decanal, indicated potential interaction sites of aldehyde substrates with the aldehyde binding site of bacterial luciferases. The in vivo relevance of the results is discussed.

Aldehydes↗
PubMed1995

Aldehyde dehydrogenase activity of Drosophila melanogaster alcohol dehydrogenase: burst kinetics at high pH and aldehyde dismutase activity at physiological pH.

The ability of Drosophila alcohol dehydrogenase (D-ADH) to catalyze the oxidation of aldehydes to carboxylic acids has been re-examined. Prior studies are shown to have been compromised by a nonenzymic reaction between the aldehydic substrates and amine-containing buffers, e.g., glycine or Tris, and an amine-catalyzed addition of aldehyde to NAD+. These reactions interfere with spectrophotometric assays for monitoring aldehyde oxidation and obscure the nature and scope of D-ADH-catalyzed aldehyde oxidation, particularly at physiological pH. Use of nonreactive buffers, such as pyrophosphate or phosphate, and 1H NMR spectroscopy to monitor all the components of the reaction mixture reveals the facile dismutation of aldehydes into equimolar quantities of the corresponding acids and alcohols at both neutral and high pH. At high pH, dismutation is accompanied by a small burst of NADH production to a steady-state concentration ( < 10 microM) that represents a partitioning between NADH dissociation and aldehyde reduction. The increase in A340 is therefore not a direct measure of the aldehyde oxidation reaction, and the resulting kinetic values cannot be compared to those for alcohol dehydrogenation. The present results for D-ADH, combined with data from the literature, establish that aldehyde oxidation, manifest as dismutation, is a widespread property of alcohol dehydrogenases with potential physiological importance in alcohol metabolism and aldehyde detoxification.

Alcohol Dehydrogenase↗
PubMed1997

Isolation of animal cell mutants defective in long-chain fatty aldehyde dehydrogenase. Sensitivity to fatty aldehydes and Schiff's base modification of phospholipids: implications for Sj-ogren-Larsson syndrome.

Using tritium suicide, we have isolated a variant of the Chinese hamster ovary cell line, CHO-K1, that is deficient in long-chain fatty alcohol:NAD+ oxidoreductase (FAO; EC 1.1.1.192). Specifically, it was the fatty aldehyde dehydrogenase component that was affected. The enzymatic deficiency found in this mutant strain, designated FAA. K1A, was similar to that displayed by fibroblasts from patients with Sjögren-Larsson syndrome (SLS), an inheritable neurocutaneous disorder. Complementation analyses suggested that the deficiency in fatty alcohol oxidation in the FAA.K1A cells and the SLS fibroblasts is a result of lesions in homologous genes. The FAA.K1A cells were unable to convert long chain fatty aldehydes to the corresponding fatty acids. This resulted in a hypersensitivity of the FAA.K1A cells to the cytotoxic effects of long chain fatty aldehydes. The difference between the mutant and wild-type cells was most obvious when using fatty aldehydes between 14 and 20 carbons, with the greatest difference between wild-type and mutant cells found when using octadecanal. Fibroblasts from a patient with SLS also displayed the hypersensitivity phenotype when compared with FAldDH+ human fibroblasts. In both CHO and human FAldDH- cell lines, addition of long chain fatty aldehydes to the medium caused a dramatic increase in aldehyde-modified phosphatidylethanolamine, presumably through Schiff's base addition to the primary amine of the ethanolamine head group. When 25 microM hexadecanal was added to the growth medium, approximately 10% of the phosphatidylethanolamine was found in the fatty aldehyde-modified form in FAA.K1A, although this was not observed in wild-type cells. Modified phosphatidylethanolamine could be detected in FAldDH- cells even when exogenous fatty aldehydes were not added to the medium. We propose a possible role for fatty aldehydes, or other aldehydic species, in mediating some of the symptoms associated with Sjögren-Larsson syndrome.

Aldehyde Oxidoreductases↗
PubMed1981

Fatty acid reductase in bioluminescent bacteria. Resolution from aldehyde reductases and characterization of the aldehyde product.

Fatty acid reductase from the bioluminescent bacterium Photobacterium phosphoreum, has been partially purified free of aldehyde reductase activity and with a low endogenous fatty acid content permitting the characterization of the aldehyde product of the reaction. Two aldehyde reductases, both dependent on NADH, were separated by anion-exchange chromatography from the fatty acid reductase activity. The partially purified fatty acid reductase catalyzed the synthesis exclusively of long chain aldehydes from fatty acids in the presence of ATP and NADPH as demonstrated by the conversion of [3H]tetradecanoic acid to [3H]aldehyde. Comparison of the amount of [3H]aldehyde produced with the bioluminescence responses of luciferase to the aldehyde product and standard aldehydes, both with respect to maximum light intensity and luminescent decay, established that tetradecanoic acid has been converted to tetradecanal, the aldehyde of the same chain length. These results are consistent with a mechanism involving activation of the fatty acid with ATP followed by reduction of a fatty acyl intermediate to the corresponding aldehyde.

Aldehyde Oxidoreductases↗
PubMed1987

Substituent effects during the rat liver aldehyde dehydrogenase catalyzed oxidation of aromatic aldehydes.

The influence of the steric hindrance of halogen substituents was investigated in vitro by measuring the activity of yeast aldehyde dehydrogenase (aldehyde: NAD(P)+ oxidoreductase, EC 1.2.1.5) and of aldehyde dehydrogenases in subcellular rat liver fractions with a series of ortho- and para-halo-substituted benzaldehydes as substrates. Upon an increase in the size of the halogen substituent (F, Cl, Br), the reactivity of yeast aldehyde dehydrogenase to ortho-substituted benzaldehydes decreased drastically. The same phenomenon was observed with the unspecific aldehyde dehydrogenases in three rat liver fractions; cytoplasm, mitochondria and microsomes. The corresponding para-halobenzaldehydes (F, Cl, Br, I) did not reveal large differences in reactivity to the various rat liver aldehyde dehydrogenases. The aldehyde dehydrogenases in the rat liver microsomal fraction exhibited most clearly the regiospecificity. Enzymatic oxidation of 4-bromobenzaldehyde was more than 30-times faster then the ortho-isomer. The findings in this investigation confirm the suggestion that the steric hindrance of bulky ortho-substituents of benzaldehydes account for the slowing down of the aldehyde dehydrogenase-catalyzed oxidation of benzaldehydes to corresponding benzoic acids. The enzymatic oxidation of microsomal aldehyde dehydrogenase is strongly influenced by steric effects of benzaldehydes, bearing a halogen in ortho-position. We think that the microsomal aldehyde dehydrogenase might be the principal enzyme responsible for oxidation of halobenzaldehydes in rat liver.

Aldehyde Dehydrogenase↗
PubMed1994

Role of aldehyde metabolizing enzymes in mediating effects of aldehyde products of lipid peroxidation in liver cells.

It is well established that many types of tumor cells have reduced lipid peroxidation capacity compared to their normal counterparts. Changes in the activity of enzymes metabolizing aldehydes produced by lipid peroxidation have also been reported in a variety of tumor cells. We have investigated the relationship between changes in lipid peroxidation and changes in aldehyde-metabolizing enzymes in normal hepatocytes and two representative rat hepatoma cell lines, McA-RH-7777 and JM2. Compared to hepatocytes, both 7777 and JM2 cells have significantly lower basal and prooxidant-induced levels of lipid peroxidation than normal hepatocytes. Using 4-hydroxynonenal (4-HNE) as substrate, both cell lines also have significantly reduced activities of alcohol dehydrogenase (ADH) and glutathione S-transferase (GST) compared to hepatocytes. JM2 cells have significantly increased aldehyde dehydrogenase (ALDH) and aldehyde reductase (ALRD) activities with 4-HNE. In 7777 cells the ALDH and ALRD activities are not different from hepatocytes. The changes in enzyme activity are inversely correlated with the sensitivity of cells to 4-HNE. JM2 cells, with increased ALDH and ALRD and decreased ADH and GST, are much more resistant to the toxic effects of 4-HNE than 7777 cells. Normal hepatocytes and JM2 cells are approximately equally resistant to 4-HNE even though hepatocytes rely primarily on GST-mediated aldehyde conjugation to metabolize 4-HNE. Coupled with previous results from our laboratories, the overall increased sensitivity of certain hepatoma cells to lipid aldehydes appears due to decreased ability of these hepatoma cells to remove toxic products of lipid peroxidation. Moreover, hepatoma cells with increased levels of aldehyde dehydrogenase and aldehyde reductase appear most like hepatocytes in their ability to metabolize lipid aldehydes.

Aldehyde Dehydrogenase↗
PubMed1984

Vibrio harveyi aldehyde dehydrogenase. Partial reversal of aldehyde oxidation and its possible role in the reduction of fatty acids for the bioluminescence reaction.

Vibrio harveyi aldehyde dehydrogenase, which catalyzes the oxidation of long chain aliphatic aldehydes to acids, has been discovered to have both acyl-CoA reductase and thioesterase activities. Tetradecanoyl-CoA was reduced to tetradecanal in the presence of NAD(P)H, as monitored by the stimulation of luciferase activity by the aldehyde product (acyl-CoA reductase). In the absence of NADPH, [3H]tetradecanoyl-CoA was hydrolyzed to the hexane-soluble fatty acid (thioesterase). Inhibition data with N-ethylmaleimide suggest that a single active site on aldehyde dehydrogenase is responsible for all three enzymatic activities. The acyl-CoA reductase activity was maximal at low NADPH concentration (about 1 microM), whereas much higher concentrations of NADH (greater than 100-fold) were required for optimal activity. Further increases in NADPH or NADH concentrations inhibited both the acyl-CoA reductase and thioesterase reactions. On the basis of the specificity of aldehyde dehydrogenase for NADP(H), an improved purification procedure employing affinity chromatography on 2', 5'-ADP-Sepharose is described. Although fatty acid reductase activity could not be reconstituted, aldehyde dehydrogenase specifically stimulated the rate of acylation of the acyl protein synthetase component from the Photobacterium phosphoreum fatty acid reductase system. This observation, combined with the partial reversal of aldehyde oxidation described above, suggests a possible role for aldehyde dehydrogenase in aldehyde biosynthesis for the luminescent reaction in V. harveyi.

Acyl Coenzyme A↗
PubMed1988

Aldehyde pararosanilin (true aldehyde fuchsin) stains purified insulin, oxidized or not, following adequate fixation with either formalin or Bouin's fluid.

Gomori reported that aldehyde fuchsin stained the granules of pancreatic islet beta cells selectively and without need of permanganate pretreatment. Others adopted permanganate oxidation because it makes staining faster though much less selective. All aldehyde fuchsins are not equivalent, being made from "basic fuchsin" whose composition may vary from pure pararosanilin to one of its methylated homologs, rosanilin or a mixture. Mowry et al. have shown that only aldehyde fuchsin made from pararosanilin stained unoxidized pancreatic beta cells (PBC). Aldehyde fuchsins made from methylated homologs of pararosanilin stain PBC cells only after oxidation, which induces basophilia of other cells as well; these are less selective for PBC. Is the staining of PBC by aldehyde fuchsins due to insulin? Others have been unable to stain pure insulin with aldehyde fuchsins except in polyacrylamide gels and only after oxidation with permanganate. They have concluded that insulin contributed to the staining of oxidized but not of unoxidized PBC. This view denies any inherent validity of the more selective staining of unoxidized PBC cells as an indication of their insulin content. We describe here indisputable staining of unoxidized pure insulins by aldehyde fuchsin made with pararosanilin. Dried spots of insulin dissolved in the stain unless fixed beforehand. Spots of dried insulin solution made on various support media and fixed in warm formalin vapor were colored strongly by the stain. Insulin soaked Gelfoam sponges were dried, fixed in formalin vapor and processed into paraffin. In unoxidized paraffin sections, presumed insulin inside gel spaces was stained strongly by aldehyde pararosanilin. Finally, the renal tubules of unoxidized paraffin sections of kidneys from insulin-injected mice fixed in either Bouin's fluid or formalin were loaded with material stained deeply by aldehyde pararosanilin. This material was absent in renal tubules of mice receiving no insulin. The material in the spaces of insulin-soaked gels and in the renal tubules of insulin-injected mice was proven to be insulin by specific immunostaining of duplicate sections. The same material was also stained by aldehyde pararosanilin used after permanganate. So, this dye stains oxidized or unoxidized insulin if fixed adequately.

Acetates↗
PubMed1989

Oxidation of aldehydic products of lipid peroxidation by rat liver microsomal aldehyde dehydrogenase.

Lipid peroxidation in microsomal membranes produces a large number of aldehydes, alcohols, and ketones, some of which have been shown to be cytotoxic. This study has determined the kinetic parameters for the oxidation of aldehyde lipid peroxidation products by purified rat hepatic microsomal aldehyde dehydrogenase (ALDH). Livers were obtained from male Sprague-Dawley rats for preparation of microsomal ALDH which was purified 400-fold. Kinetic parameters, Vmax and V/K, were determined for saturated and unsaturated aldehydes of three to nine carbons in length in the presence of NAD+. Of the aldehydes examined, only acrolein and 4-hydroxynonenal were not oxidized by ALDH. The Vmax values (mumol NADH produced/min/mg protein) increased linearly with carbon chain length and ranged from 6.5 to 23 for the saturated series and 4.0 to 9.0 for the unsaturated aldehydes. The affinity constant V/K (nmol NADH produced/min/mg protein/nmol aldehyde/liter) also increased with carbon chain length and ranged from 12 to 9000 for the saturated aldehydes and 13 to 5300 for the unsaturated aldehydes. These results suggest that microsomal ALDH may serve a biological role for detoxification of reactive aldehydes produced by lipid peroxidation of microsomal membranes.

Alcohol Dehydrogenase↗