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PubMed2003

Soehngenia saccharolytica gen. nov., sp. nov. and Clostridium amygdalinum sp. nov., two novel anaerobic, benzaldehyde-converting bacteria.

Two anaerobic, benzaldehyde-converting bacteria were isolated from an anaerobic upflow anaerobic sludge bed (UASB)-reactor treating potato starch waste water. Strain BOR-Y(T) converted benzaldehyde to benzoate and benzylalcohol in approximately equimolar concentrations. Benzaldehyde conversion did not support growth. Strain BOR-Y(T) was Gram-positive and rod-shaped, and its cells were slightly thickened in the middle. The strain was a mesophilic spore-former that grew between 15 and 40 degrees C, with optimum growth at 30-37 degrees C. The optimum pH for growth was pH 7.0. Strain BOR-Y(T) grew on a wide range of carbohydrates and some other carbon sources including yeast extract, cysteine and serine. The G+C content of its DNA was 42 mol%. According to physiological characteristics and 16S rRNA gene sequence analysis, confirmed by DNA-DNA hybridization with its phylogenetic neighbours, strain BOR-Y(T) belongs to a novel genus of cluster XII of the clostridia, namely Soehngenia; the name Soehngenia saccharolytica is proposed for the type species (type strain BOR-Y(T)=DSM 12858(T)=ATCC BAA-502(T)). Strain BR-10(T) reduced benzaldehyde to benzylalcohol. This conversion was coupled to growth. In a medium containing yeast extract, the presence of benzaldehyde resulted in the accumulation of more than twofold more cells. Strain BR-10(T) was a Gram-positive organism that was characterized by oval- or rod-shaped cells with oval ends, which occurred singly, in pairs or sometimes in chains. The strain was moderately thermophilic and grew between 20 and 60 degrees C, with optimum growth at 45 degrees C. The optimum pH for growth was between pH 7.0 and 7.5. Strain BR-10(T) grew on a wide range of carbon sources including carbohydrates, yeast extract, casein and some amino acids. The G+C content of its DNA was 32 mol%. As determined by 16S rRNA gene sequence analysis, strain BR-10(T) represents a novel species of cluster XIVa of the clostridia; the name Clostridium amygdalinum is proposed for this novel species (type strain BR-10(T)=DSM 12857(T)=ATCC BAA-501(T)).

Anaerobiosis↗
PubMed2004

Kinetics and specificity of guinea pig liver aldehyde oxidase and bovine milk xanthine oxidase towards substituted benzaldehydes.

Molybdenum-containing enzymes, aldehyde oxidase and xanthine oxidase, are important in the oxidation of N-heterocyclic xenobiotics. However, the role of these enzymes in the oxidation of drug-derived aldehydes has not been established. The present investigation describes the interaction of eleven structurally related benzaldehydes with guinea pig liver aldehyde oxidase and bovine milk xanthine oxidase, since they have similar substrate specificity to human molybdenum hydroxylases. The compounds under test included mono-hydroxy and mono-methoxy benzaldehydes as well as 3,4-dihydroxy-, 3-hydroxy-4-methoxy-, 4-hydroxy-3-methoxy-, and 3,4-dimethoxy-benzaldehydes. In addition, various amines and catechols were tested with the molybdenum hydroxylases as inhibitors of benzaldehyde oxidation. The kinetic constants have shown that hydroxy-, and methoxy-benzaldehydes are excellent substrates for aldehyde oxidase (Km values 5x10(-6) M to 1x10(-5) M) with lower affinities for xanthine oxidase (Km values around 10(-4) M). Therefore, aldehyde oxidase activity may be a significant factor in the oxidation of the aromatic aldehydes generated from amines and alkyl benzenes during drug metabolism. Compounds with a 3-methoxy group showed relatively high Vmax values with aldehyde oxidase, whereas the presence of a 3-hydroxy group resulted in minimal Vmax values or no reaction. In addition, amines acted as weak inhibitors, whereas catechols had a more pronounced inhibitory effect on the aldehyde oxidase activity. It is therefore possible that aldehyde oxidase may be critical in the oxidation of the analogous phenylacetaldehydes derived from dopamine and noradrenaline.

Aldehyde Oxidase↗
PubMed1988

Therapy of P388 leukemia with benzaldehyde.

Optimal schedules of benzaldehyde (50-100 mg kg-1 intraperitoneally) on day 1 or on several days after inoculation of 10(5) P388 leukemia cells to DBA 2J mice increased survival by 70-100%. No significant prolongation of survival was observed between the various schedules of benzaldehyde treatment. Significantly longer survival was observed on day 30 after benzaldehyde treatment with 100 mg kg-1 on day 1 or 50 mg kg-1 on days 1-4 as compared to untreated controls, but no cure was achieved with any schedule and dose of benzaldehyde. No or minimal activity of benzaldehyde on L1210 and L5178Y leukemias, Ehrlich adenocarcinoma and Yoshida sarcoma was observed.

Animals↗
PubMed1985

4,6-Benzylidene-D-glucose, a benzaldehyde derivative that inhibits protein synthesis but not mitosis of NHIK 3025 cells.

The effect of the benzaldehyde derivative 4,6-benzylidene-D-glucose (BG) on cell-cycle kinetics, protein synthesis, and cell survival of human NHIK 3025 cells has been investigated. The effects are compared with results reported previously for benzaldehyde, which was shown to inhibit protein synthesis as well as induce metaphase inhibition. BG exerted an effect on protein synthesis similar to that of benzaldehyde, but did not affect metaphase. Inhibition of protein synthesis was measured as a reduction in the rate of incorporation of [3H]valine and is thus a measure of the rate of total protein synthesis. The quantitative effect on the rate of protein synthesis was equal for the two drugs when compared on a concentration basis. Both drugs induced inhibition of cell-cycle progression during interphase, which is thought to be a secondary result of the protein synthesis inhibition. The concentration of BG and the hydrolysis product benzaldehyde were determined in cell culture medium by high-performance liquid chromatography. BG was not found to be hydrolyzed to free benzaldehyde when in contact with cells or in a cell sonicate. The results indicate that BG is not metabolized but acts in the form of BG.

Benzaldehydes↗
PubMed2001

Reactions of PhSCH(2)Li and NCCH(2)Li with benzaldehyde and benzophenone: when does the mechanism change from ET to polar?

The carbonyl-carbon kinetic isotope effect (KIE) and the substituent effect were measured for the reaction of phenylthiomethyllithium (PhSCH(2)Li, 1) with benzaldehyde and benzophenone, and cyanomethyllithium (NCCH(2)Li, 2) with benzaldehyde, and the results were compared with those for other lithium reagents such as MeLi, PhLi, CH(2)=CHCH(2)Li, and CH(2)=C(OLi)C(CH(3))(3). It was previously shown that the reactions of MeLi, PhLi, and CH(2)=CHCH(2)Li proceed via a rate-determining electron transfer (ET) process whereas the reaction of lithium pinacolone enolate goes through the polar (PL) mechanism. The reaction of 1 with benzaldehyde gave no carbonyl-carbon KIE ((12)k/(13)k = 0.999 +/- 0.004), similar to that measured previously for the MeLi reaction with benzophenone ((12)k/(14)k = 1.000). The effect of substituents of the aromatic ring of benzaldehyde and benzophenone on the reactivity gave very small Hammett rho values of 0.17 +/- 0.03 and 0.26 +/- 0.05, respectively. These small rho values are again similar to that observed for the reaction of MeLi. Likewise the reactions of 2 with benzaldehydes gave small KIE and the rho value ((12)k/(13)k = 0.996 +/- 0.004, rho = 0.14 +/- 0.02). Dehalogenation and enone-isomerization probe experiments for 2 showed no evidence for the presence of radical-ion pair of sufficient lifetime during the course of the reaction. It is concluded that the reactions of 1 and 2 with the aromatic carbonyl compounds proceed via the electron transfer-radical coupling mechanism with rate-determining ET as in the reactions of MeLi, PhLi, and CH(2)=CHCH(2)Li.

Journal Article↗
PubMed2005

Hydrogenation of benzaldehyde and cinnamaldehyde in compressed CO2 medium with a Pt/C catalyst: a study on molecular interactions and pressure effects.

The hydrogenation of benzaldehyde and cinnamaldehyde has been studied with a 5% Pt/C catalyst in compressed CO(2). The effect of CO(2) pressure on the total conversion was found to be different between the two aldehydes. The total conversion of benzaldehyde merely decreases with increasing CO(2) pressure, while that of cinnamaldehyde shows a maximum at a certain pressure. High-pressure FTIR measurements indicate the existence of interactions of CO(2) with the aldehydes. The absorption of nu(C=O) red-shifts at increasing CO(2) pressure, and this red-shift is more significant for cinnamaldehyde than for benzaldehyde, indicating that the C=O bond of the former becomes more reactive than the latter. The difference in the mode of interactions of CO(2) with these aldehydes has also been indicated by changes of nu(C=O) of CO(2). Thus, the conversion of benzaldehyde will decrease with increasing CO(2) pressure because of a simple dilution by introducing a larger quantity of CO(2). For cinnamaldehyde, the conversion will increase at low pressures because of increasing interactions with CO(2) molecules (increasing the reactivity of the C=O bond) but decrease at high pressures because of the simple dilution effect, similar to the case of benzaldehyde. The dense CO(2) molecules are not likely to change the catalytic activity of supported Pt particles, which was previously suggested from optical absorption of supported fine metal (Au) particles in a compressed CO(2) medium.

Journal Article↗
PubMed1998

Conversion of phenylalanine to benzaldehyde initiated by an aminotransferase in lactobacillus plantarum

The production of benzaldehyde from phenylalanine has been studied in various microorganisms, and several metabolic pathways have been proposed in the literature for the formation of this aromatic flavor compound. In this study, we describe benzaldehyde formation from phenylalanine by using a cell extract of Lactobacillus plantarum. Phenylalanine was initially converted to phenylpyruvic acid by an aminotransferase in the cell extract, and the keto acid was further transformed to benzaldehyde. However, control experiments with boiled cell extract revealed that the subsequent conversion of phenylpyruvic acid was a chemical oxidation step. It was observed that several cations could replace the extract in the conversion of phenylpyruvic acid to benzaldehyde. Addition of Cu(II) ions to phenylpyruvic acid resulted not only in the formation of benzaldehyde, but also in the generation of phenylacetic acid, mandelic acid, and phenylglyoxylic acid. These compounds have been considered intermediates in the biological conversion of phenylalanine. The chemical conversion step of phenylpyruvic acid was dependent on temperature, pH, the availability of cations, and the presence of oxygen.

Journal Article↗
PubMed1995

Overlapping substrate specificities of benzaldehyde dehydrogenase (the xylC gene product) and 2-hydroxymuconic semialdehyde dehydrogenase (the xylG gene product) encoded by TOL plasmid pWW0 of Pseudomonas putida.

Two aldehyde dehydrogenases involved in the degradation of toluene and xylenes, namely, benzaldehyde dehydrogenase and 2-hydroxymuconic semialdehyde dehydrogenase, are encoded by the xylC and xylG genes, respectively, on TOL plasmid pWW0 of Pseudomonas putida. The nucleotide sequence of xylC was determined in this study. A protein exhibiting benzaldehyde dehydrogenase activity had been purified from cells of P. putida (pWW0) (J. P. Shaw and S. Harayama, Eur. J. Biochem. 191:705-714, 1990); however, the amino-terminal sequence of this protein does not correspond to that predicted from the xylC sequence but does correspond to that predicted from the xylG sequence. The protein purified in the earlier work was therefore 2-hydroxymuconic semialdehyde dehydrogenase (the xylG gene product). This conclusion was confirmed by the fact that this protein oxidized 2-hydroxymuconic semialdehyde (kcat/Km = 1.6 x 10(6) s-1 M-1) more efficiently than benzaldehyde (kcat/Km = 3.2 x 10(4) s-1 M-1). The xylC product, the genuine benzaldehyde dehydrogenase, was purified from extracts of P. putida (pWW0-161 delta rylG) which does not synthesize 2-hydroxymuconic semialdehyde dehydrogenase. The amino-terminal sequence of the purified protein corresponds to the amino-terminal sequence deduced from the xylC sequence. This enzyme efficiently oxidized benzaldehyde (kcat/Km = 1.7 x 10(7) s-1 M-1) and its analogs but did not oxidize 2-hydroxymuconic semialdehyde or its analogs.

Alcohol Oxidoreductases↗
PubMed2002

Enzymatic (R)-phenylacetylcarbinol production in benzaldehyde emulsions.

(R)-Phenylacetylcarbinol [(R)-PAC)] is the chiral precursor for the production of the pharmaceuticals ephedrine and pseudoephedrine. Reaction conditions were improved to achieve increased (R)-PAC levels in a simple batch biotransformation of benzaldehyde emulsions and pyruvate, using partially purified pyruvate decarboxylase (PDC) from the filamentous fungus Rhizopus javanicus NRRL 13161 as the catalyst. Lowering the temperature from 23 degrees C to 6 degrees C decreased initial rates but increased final (R)-PAC concentrations. Addition of ethanol, which increases benzaldehyde solubility, was not beneficial for (R)-PAC production. It was established that proton uptake during biotransformation increases the pH above 7 thereby limiting (R)-PAC production. For small-scale studies, biotransformations were buffered with 2-2.5 M MOPS (initial pH 6.5). High concentrations of MOPS as well as some alcohols and KCl stabilised PDC. A balance between PDC and substrate concentrations was determined with regards to ( R)-PAC production and yields on enzyme and substrates. R. javanicus PDC (7.4 U/ml) produced 50.6 g/l (337 mM) ( R)-PAC in 29 h at 6 degrees C with initial 400 mM benzaldehyde and 600 mM pyruvate. Molar yields on consumed benzaldehyde and pyruvate were 97% and 59%, respectively, with 17% pyruvate degraded and 24% converted into acetaldehyde and acetoin; 43% PDC activity remained, indicating reasonable enzyme stability at high substrate and product concentrations.

Acetone↗
PubMed2005

Enzymatic (R)-phenylacetylcarbinol production in a benzaldehyde emulsion system with Candida utilis cells.

Recent progress in enzymatic (R)-phenylacetylcarbinol (PAC) production has established the need for low cost and efficient biocatalyst preparation. Pyruvate decarboxylase (PDC) added in the form of Candida utilis cells showed higher stability towards benzaldehyde and temperature in comparison with partially purified preparations. In the presence of 50 mM benzaldehyde and at 4 degrees C, a half-life of 228 h was estimated for PDC added as C. utilis cells, in comparison with 24 h for the partially purified preparation. Increasing the temperature from 4 to 21 degrees C for PAC production with C. utilis cells resulted in similar final PAC levels of 39 and 43 g l(-1) (258 and 289 mM), respectively, from initial 300 mM benzaldehyde and 364 mM pyruvate. The overall volumetric productivity was enhanced 2.8-fold, which reflected the 60% shorter reaction time at the higher temperature. Enantiomeric excess values of 98 and 94% for R-PAC were obtained at 4 and 21 degrees C, respectively, and benzyl alcohol (a potential by-product from benzaldehyde) was not formed.

Acetone↗
PubMed2001

Biotransformation of benzaldehyde into (R)-phenylacetylcarbinol by filamentous fungi or their extracts.

Extracts of 14 filamentous fungi were examined regarding their potential for production of (R)-phenylacetylcarbinol [(R)-PAC], which is the chiral precursor in the manufacture of the pharmaceuticals ephedrine and pseudoephedrine. Benzaldehyde and pyruvate were transformed at a scale of 1.2 ml into PAC by cell-free extracts of all selected strains, covering the broad taxonomic spectrum of Ascomycota, Zygomycota and Basidiomycota. Highest final PAC concentrations were obtained with the extracts of Rhizopus javanicus and Fusarium sp. [78-84 mM (11.7-12.6 g/l) PAC within 20 h from initial substrate concentrations of 100 mM benzaldehyde and 150 mM pyruvate]. (R)-PAC was in about 90-93% enantiomeric excess. Rhizopus javanicus had the advantage of faster growth than Fusarium sp. Rhizopus javanicus mycelia were used as an example in a biotransformation process based on whole cells and benzaldehyde and glucose as substrates. The substrate pyruvate was generated through the fungal fermentation of glucose. Only 19 mM PAC (2.9 g/l) were produced within 8 h from 80 mM benzaldehyde. with evidence of significant benzyl alcohol production.

Acetone↗
PubMed1983

Remarkable positional (regio)specificity of xanthine oxidase and some dehydrogenases in the reactions with substituted benzaldehydes.

Upon an increase in the size of the substituent, the reactivity of xanthine oxidase to ortho-substituted benzaldehydes drastically decreases while that to para-substituted benzaldehydes does not change significantly. The enzyme exhibits this regiospecificity with respect to both electron-withdrawing substituents (e.g., halogens) and electron-donating ones (alkyls and alkoxyls). Xanthine oxidase-catalyzed oxidation of m- and p-nitrobenzaldehyde is more than 300-times faster than that of the o-isomer, whereas the rates of their non-enzymatic oxidation are comparable, as are the rates of the enzymatic oxidation of p- and o-nitrocinnamaldehyde. These and other findings of this work indicate that the discovered positional specificity of xanthine oxidase is due to steric hindrances in the reaction of the enzyme's active center with the aldehyde moiety having a bulky substituent in its close proximity. Such regiospecificity of the enzyme exists regardless of the nature of the electron acceptor used and can be employed for the separation of mixtures of positional isomers of substituted benzaldehydes. A marked positional specificity in the xanthine oxidase-catalyzed oxidation of substituted benzaldehydes appears to be a rather general phenomenon: three other enzymes tested, alcohol dehydrogenases from horse liver and yeast and aldehyde dehydrogenase from yeast, all follow a similar pattern in the reactions with para- and ortho-substituted halobenzaldehydes.

Alcohol Dehydrogenase↗
PubMed1991

Structure-activity correlations in human kidney aldehyde reductase-catalyzed reduction of para-substituted benzaldehyde by 3-acetyl pyridine adenine dinucleotide phosphate.

Steady-state kinetic parameters of the human kidney aldehyde reductase-catalyzed reduction of para-substituted benzaldehydes by 3-acetyl pyridine dinucleotide phosphate (3-APADPH) were determined. The kcat of aldehyde reduction by 3-APADPH was 2- to 4-fold lower than by NADPH. The dissociation constant of 3-APADPH from the enzyme-coenzyme complex was higher (77 microM) than that of NADPH (5.3 microM). Primary deuterium kinetic isotope effects on both kcat and kcat/Km for para-substituted benzaldehyde reduction by 3-APADPH (with the exception of para-carboxybenzaldehyde) were equal and on average 2.82 +/- 0.21, suggesting that these reactions follow a rapid equilibrium-ordered reaction scheme in which the hydride transfer step is rate-limiting. Multiple regression analysis of the data suggests that benzaldehyde reduction depends upon electronic substituent effects, characterized by a rho value of 0.5. These data are consistent with a transition state in which the charge on the aldehyde carbonyl increases relative to the charge on this group in the ground state. A positive deviation of para-carboxybenzaldehyde from the linear correlation between other benzaldehydes and the substituent constant sigma + suggests a specific interaction of the carboxyl substituent of the substrate with the enzyme.

Alcohol Dehydrogenase↗
PubMed1995

Inhibition of metabolism of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone by dietary benzaldehydes.

As part of a routine screening assay, benzaldehyde was found to inhibit 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) metabolism. Consequently, the effects of benzaldehyde and several structurally related compounds on NNK metabolism were examined in murine hepatic and pulmonary microsomes. All test compounds inhibited formation of the metabolites 4-oxo-4-(3-pyridyl)butyric acid (OPBA), 4-hydroxy-1-(3-pyridyl)-1-butanone (HPB), and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) in hepatic microsomes and inhibited formation of 4-(methylnitrosamino)-1-(3-pyridyl-N-oxide)-1-butanone (NNK N-oxide), HPB, and NNAL in pulmonary microsomes. m-Anisaldehyde was the most potent inhibitor, and p-hydroxybenzaldehyde and syringaldehyde were less potent than benzaldehyde and vanillin in inhibiting the formation of OPBA and HPB, NNK metabolites that reflect metabolic activation (alpha-hydroxylation). Vanillin was essentially as potent as benzaldehyde. The mechanism of inhibition exhibited by these compounds appears to be competitive in nature. The ability of these compounds to inhibit NNK activation suggests that these compounds may be effective blocking agents (anti-initiating agents) for NNK lung tumorigenesis.

Animals↗
PubMed2002

Polarographic determination of benzaldehyde in benzyl alcohol and sodium diclofenac injection formulations.

A rapid and sensitive polarographic method was developed for qualitative as well as quantitative analysis of the neurotoxic contaminant benzaldehyde in Na-diclofenac injections and in benzyl alcohol used for parental formulations. A well-defined differential pulse (DP) polarographic peak or a sampled direct current (SDC) wave was obtained at -1.39 V (vs. silver-silver chloride reference electrode) in Britton-Robinson buffer (pH 9.15) and at -1.41 V in 0.1 M LiCl solution. The reduction step involves a two-electron process, corresponding to the formation of benzyl alcohol. No peaks were observed in the anodic branch of the cyclic voltammogram, emphasizing the occurrence of an irreversible process. The peak current versus concentration relationship was found to be linear up to 50 microg/ml with the detection limit of 10 ng/ml and quantitation limit of 30 ng/ml. The relative standard deviations (S.D.) obtained for concentration levels of benzaldehyde as low as 25 microg/ml with the SDC and DP methods were 1.5 and 0.78% (n=10), respectively. Benzyl alcohol and Na-diclofenac are not electrochemically active, and metabisulfite reductions at -0.664 and -1.240 V do not interfere with the benzaldehyde reduction peak. The proposed methods (DP and SDC polarography) have been applied satisfactorily to the determination of benzaldehyde traces in benzyl alcohol and in different pharmaceutical products such as Na-diclofenac injectable formulations.

Benzaldehydes↗
PubMedDate not supplied

Synthesis of heterotelechelic poly(ethylene glycol) derivatives having alpha-benzaldehyde and omega-pyridyl disulfide groups by ring opening polymerization of ethylene oxide using 4-(diethoxymethyl)benzyl alkoxide as a novel initiator.

New heterotelechelic PEG-containing benzaldehyde and 2-pyridyldithio endgroup (CHO-Bz-PEG-SSpyl) was synthesized with high efficiency and high selectivity. An alpha-benzylacetal-omega-methansulfonyl PEG was prepared as the first step to CHO-Bz-PEG-SSpyl through the ring-opening polymerization of ethylene oxide (EO) initiated by potassium 4-(diethoxymethyl)benzyl alkoxide (PDA), followed by the successive conversion of the end-alkoxide group to a methanesulfonyl group and then to dithiocarbonate derivative. Further, deprotection of the dithiocarbonate derivative and subsequent conversion to the 2-pyridyldithio group at the omega-end was successfully performed through a one-step reaction to form alpha-benzylacetal-omega-2-pyridyldithio PEG (aceBz-PEG-SSpyl). The aceBz-PEG-SSpyl was then treated with an aqueous HCl solution (pH 5.0) to generate the benzaldehyde group at the alpha-end. Molecular functionalities of the benzaldehyde and the 2-pyridyldithio end group of the heterotelechelic PEG (CHO-Bz-PEG-SSpyl) thus prepared were characterized by (1)H and (13)C NMR, showing that the reaction proceeded almost quantitatively. The benzaldehyde end group is available to conjugate various ligands having a primary amino group by forming the pH-sensitive imine linkage (-N=CHC(6)H(4)-).

Benzaldehydes↗
PubMed1993

Alternative pathways and reactions of benzyl alcohol and benzaldehyde with horse liver alcohol dehydrogenase.

Liver alcohol dehydrogenase catalyzes the reaction of NAD+ and benzyl alcohol to form NADH and benzaldehyde by a predominantly ordered reaction. However, enzyme-alcohol binary and abortive ternary complexes form at high concentrations of benzyl alcohol, and benzaldehyde is slowly oxidized to benzoic acid. Steady-state and transient kinetic studies, equilibrium spectrophotometric measurements, product analysis, and kinetic simulations provide estimates of rate constants for a complete mechanism with the following reactions: (1) E<-->E-NAD+<-->E-NAD(+)-RCH2OH<-->E-NADH-RCHO<-->E-NADH<-->E ; (2) E-NADH<-->E-NADH-RCH2OH<-->E-RCH2OH<-->E; (3) E-NAD+<-->E-NAD(+)-RCHO-->E- NADH-RCOOH<-->E-NADH. The internal equilibrium constant for hydrogen transfer determined at 30 degrees C and pH 7 is about 5:1 in favor of E-NAD(+)-RCH2OH and has a complex pH dependence. Benzyl alcohol binds weakly to free enzyme (Kd = 7 mM) and significantly decreases the rates of binding of NAD+ and NADH. The reaction of NAD+ and benzyl alcohol is therefore kinetically ordered, not random. High concentrations of benzyl alcohol (> 1 mM) inhibit turnover by formation of the abortive E-NADH-RCH2-OH complex, which dissociates at 0.3 s-1 as compared to 6.3 s-1 for E-NADH. The oxidation of benzaldehyde by E-NAD+ (Km = 15 mM, V/E = 0.4 s-1) is inefficient relative to the oxidation of benzyl alcohol (Km = 28 microM, V/E = 3.1 s-1) and leads to a dismutation (2RCHO-->RCH2OH + RCOOH) as E-NADH reduces benzaldehyde. The results provide a description of final product distributions for the alternative reactions catalyzed by the multifunctional enzyme.

Alcohol Dehydrogenase↗
PubMed2002

Decrease in ovalbumin-induced pulmonary allergic response by benzaldehyde but not acetaldehyde exposure in a Guinea pig model.

The pulmonary effects of two environmentally relevant aldehydes were investigated in nonsensitized or ovalbumin (OA)-sensitized guineapigs (GPs). Four-week-old male Hartley GPs, weighing about 400 g, were intraperitoneally injected with 1 ml of an NaCl solution containing 100 microg OA and 100 mg Al(OH)(3). They were then exposed to either acetaldehyde (200 ppb) or benzaldehyde (500 ppb) for 4 wk (6 h/d, 5 d/wk). At the end of exposure, GPs were challenged with an OA aerosol (0.1% in NaCl) and pulmonary functions were measured. The day after, guinea pigs were anesthetized and several endpoints related to inflammatory and allergic responses were assessed in blood, whole-lung histology, and bronchoalveolar lavage (BAL). Sensitized nonexposed GPs showed bronchial hyperresponsiveness to OA and an increased number of eosinophils in blood and BAL, together with a rise in total protein and leukotrienes (LTB(4) and LTC(4)/D(4)/E(4)) in BAL. In nonsensitized GPs, exposure to acetaldehyde or benzaldehyde did not induce any change in the tested parameters, with the exception of irritation of the respiratory tract as detected by histology and an increased number of alveolar macrophages in animals exposed to acetaldehyde. In sensitized GPs, exposure to acetaldehyde induced a moderate irritation of the respiratory tract but no change in biological parameters linked to the inflammatory and allergic responses. In contrast, exposure to benzaldehyde induced a decrease both in OA-induced bronchoconstriction and in eosinophil and neutrophil numbers in BAL, an increase in the bronchodilatator mediator prostaglandin E(2) (PGE(2)), and a decrease in the bronchoconstrictor mediators LTC(4)/D(4)/E(4). Further investigations are needed to determine if the attenuated response observed in sensitized GPs exposed to benzaldehyde is due to an alteration of the mechanism of sensitization or to a more direct effect on various mechanisms of the allergic response.

Acetaldehyde↗