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PubMed1975

Procaine HCl (Gerovital H3): a weak, reversible, fully competitive inhibitor of monoamine oxidase.

A specially stabilized form of procaine hydrochloride (Gerovital H3) has been shown to be a more potent inhibitor of monoamine oxidase than procaine HCl itself and a weaker inhibitor of this enzyme than iproniazid. This preparation was studied to determine its mode of interaction with monoamine oxidase using purified rat brain mitochondrial monoamine oxidase as the enzyme source. Reaction velocities were determined spectrophotometrically by quantitating the rate of appearance of 4-hydroxyquinoline from kynuramine. Dilutional studies comparing the mechanism of inhibition of monoamine oxidase produced by Gerovital H3 and by ipronizid demonstrated that Gerovital H3 was a reversible inhibitor of monoamine oxidase. Analysis of studies using Lineweaver-Burk and Dixon plots revealed that Gerovital H3 was a fully competitive inhibitor of monoamine oxidase. That Gerovital H3 is a weak, reversible, competitive inhibitor of monoamine oxidase may explain the absence of adverse reactions associated with the clinical use of Gerovital H3 as compared to the severe adverse reactions that have been associated with the use of irreversible monoamine oxidase inhibitors.

Animals↗
PubMedDate not supplied

[Functional groups of mitochondrial monoamine oxidase].

Functional groups of mitochondrial monoamine oxidase critical for monoamine oxidase activity were investigated by chemical modification of highly purified monoamine oxidase preparations from pig liver by specific inhibitors. The substrate and inhibitory properties of synthesized derivatives of beta-phenylethylamine, containing various acylating and alkylating groups in the p-position of the benzene ring, were studied. It was shown that 4-carbmethoxy-beta-phenylethylamine (I) is readily deaminated by monoamine oxidase, whereas 4-O-acetyl-beta-phenylethylamine (II) is not affected by the enzyme. 4-O-acetyl-beta-phenylethylamine (II) and 4-ethyl-O-chloroacethyl phenol (III) inhibit deamination of tyramine, 4-amino-beta-phenylethylamine, beta-phenylethylamine, 4-chloro-beta-phenylethylamine and serotonin in different degrees. The kinetic studies demonstrated that this inhibition is probably due to the acylating properties of the compounds obtained. Selectivity in inhibition may be accounted for by acylation of the group of monoamine oxidase which is located in the nearest proximity to the nucleophynoamine oxidase which is located in the nearest proximity to the nucleophylic site of monoamine oxidase active centre important for binding of tyramine. This group is neither the imidazole group of histidyl, nor the SH-group of cysteinyl residues of monoamine oxidase protein molecule. Its nature is discussed in the light of the data obtained.

Acylation↗
PubMed2002

Cytochrome b558-dependent NAD(P)H oxidase-phox units in smooth muscle and macrophages of atherosclerotic lesions.

OBJECTIVE: Despite studies implicating superoxide anion-producing oxidases in atherosclerosis, their characteristics, expression, and regulation in cells of lesions are poorly understood. We examined the following: (1) whether cytochrome b558-dependent NAD(P)H oxidase-phox peptides are expressed by intimal smooth muscle cells (iSMCs) and macrophages of human aortic atherosclerotic lesions and their regulation and (2) whether cytochrome b558-dependent NAD(P)H oxidase represents a major NAD(P)H oxidase in iSMCs. METHODS AND RESULTS: Using a combination of immunochemical and reverse transcription-polymerase chain reaction procedures, we demonstrate that p22(phox) and gp91(phox) (cytochrome b558) expression in normal intima was restricted to a quarter of the iSMCs. In fatty streaks, a similar fraction of iSMCs expressed cytochrome b558, whereas macrophages also expressed low levels of p47(phox) and p67(phox). In fibrofatty lesions, the majority of iSMCs expressed the cytochrome b558 subunits; p67(phox) was also detected. Macrophages and macrophage-derived foam cells expressed the 4 phox subunits that constitute superoxide-producing cytochrome b558-dependent NAD(P)H oxidase. These were upregulated by transforming growth factor-beta1 and interferon-gamma. Aortic lesions also expressed Thox1 and Nox4, and although their expression also increases with lesion severity, their expression is less frequent than that of gp91(phox). CONCLUSIONS: In human aortic fibrofatty lesions, a cytochrome b558-dependent NAD(P)H oxidase appears to be a major iSMC and macrophage oxidase whose expression is upregulated by cytokines.

Adolescent↗
PubMed1997

Immunocytochemical localization on O2-sensing protein (NADPH oxidase) in chemoreceptor cells.

A potential candidate for an oxygen-sensing protein in chemoreceptor cells is a heme-linked multicomponent NADPH oxidase, originally described in neutrophils. The postulated function for the oxidase in chemoreceptor cells is to signal changes in oxygen levels (either in the blood or in the airway lumen) via changes in oxygen metabolite production. An alteration in either superoxide (or dismuted hydrogen peroxide) production may affect the gating properties of the O2-sensitive K+ channels. We have previously reported immunohistochemical localization of gp91 glycoprotein component of the oxidase to the plasma membrane of pulmonary neuroepithelial body (NEB) cells. In this study we have investigated the immunocytochemical localization of the other polypeptide components of the oxidase in NEB cells and in the glomus cells of the carotid body. Cultures of dissociated fetal rabbit NEB cells and newborn rat glomus cells were immunostained with specific antibodies recognizing the various polypeptide subunits of the oxidase using indirect immunofluorescence methods. Immunostaining with the anti-oxidase antibodies reveal strong positive reaction in both NEB and glomus cell clusters while other cells were unstained. The positive reaction product was localized to the plasma membrane and/or cytoplasm and no nuclear staining was observed. Live cell labelling studies with anti-p22 antibody showed positive immunofluorescence on the surface of NEB cells, suggesting that this component of the oxidase is also associated with the plasma membrane. In glomus cells, similar strongly positive immunofluorescence signal was observed for p22 and gp91 in paraformaldehyde-fixed cultures, regardless whether they were permeabilized or not. Taken together, our findings of cell surface localization of gp91 and p22 components of the oxidase in chemoreceptive cells suggests that the heme-linked cytochrome b558 component is associated with the plasma membrane. This association allows for direct interaction with the O2-sensitive K+ channel thus forming the molecular complex of membrane bound O2 sensor.

Animals↗
PubMed1993

Cytochrome c oxidase reaction improves histopathological assessment of zidovudine myopathy.

Zidovudine can induce a mitochondrial myopathy with ragged-red fibers and partial cytochrome c oxidase deficiency. In an attempt to improve histological assessment of zidovudine myopathy, we evaluated cytochrome c oxidase histochemical reaction in the muscle of 10 patients with biopsy-proven zidovudine myopathy (Group 1), 10 myopathic zidovudine receivers without typical histopathological features of zidovudine myopathy (Group 2), and 10 human immunodeficiency virus (HIV)-infected patients not treated by zidovudine who had an immunohistological profile of HIV-associated myopathy or other neuromuscular disorders (Group 3). Among zidovudine receivers, cytochrome c oxidase deficiency was found in 10 of 10 patients from Group 1 and 7 of 10 from Group 2. No cytochrome c oxidase deficiency was observed in patients not treated by zidovudine. When present, cytochrome c oxidase-negative fibers accounted for 2 to 28% of fibers, and there was no difference for the number of cytochrome c oxidase-negative fibers between Group 1 and Group 2. Most patients with cytochrome c oxidase deficiency that could be evaluated clinically after muscle biopsy improved after withdrawal of zidovudine (5 of 7 in Group 1, 5 of 5 in Group 2). Patients who did not improve had an HIV-associated myopathy concurrently with zidovudine myopathy. We conclude that cytochrome c oxidase reaction may be used as a reliable marker of zidovudine mitochondrial toxicity in HIV-infected patients with muscular symptoms.

Acquired Immunodeficiency Syndrome↗
PubMed1990

Activation of the superoxide-generating NADPH oxidase of macrophages by sodium dodecyl sulfate in a soluble cell-free system: evidence for involvement of a G protein.

The superoxide (O2-)-generating NADPH oxidase of resting macrophages can be activated in a soluble cell-free system by certain anionic amphiphiles, such as sodium dodecyl sulfate (SDS). We demonstrate that cell-free activation is specifically enhanced by nonhydrolyzable guanosine 5'-triphosphate (GTP) analogues. Guanosine 5'-diphosphate (GDP) and guanosine 5'-O-(2-thiodiphosphate) (GDP beta S) prevent cell-free oxidase activation and reverse the activated state when added to preactivated oxidase preparations. Nonhydrolyzable GTP analogues have a protective effect on the SDS-stimulated NADPH oxidase, as shown by the maintenance of more than 90% and close to 60% of enzyme activity 6 and 24 hr, respectively, after the addition of SDS to the cell-free preparation. A novel procedure is described for separating the activated NADPH oxidase from SDS and added nucleotides by gel filtration of the SDS-stimulated solubilized membrane-cytosol mixtures through a Sephadex G-25 column. By utilizing this method, it was found that the presence of micromolar concentrations of nonhydrolyzable GTP analogues during activation by SDS results in a marked increase in the recovery of SDS-independent, NADPH-dependent O2(-)-producing activity in the excluded volume of the column. It is suggested that GTP stabilizes the SDS-induced complex between membrane and cytosolic components of the oxidase. Cell-free activation of NADPH oxidase by SDS was found to be cholera and pertussis toxin insensitive. These results serve as evidence of the participation of a G protein in the activation of the O2(-)-generating NADPH oxidase of macrophages by SDS.

Animals↗
PubMed1995

Substrate specificity of human liver aldehyde oxidase toward substituted quinazolines and phthalazines: a comparison with hepatic enzyme from guinea pig, rabbit, and baboon.

Partially purified aldehyde oxidase (EC 1.2.3.1) has been prepared from human, rabbit, guinea pig, and baboon liver by heat treatment and precipitation with ammonium sulfate. The interaction of 35 substituted quinazolines and phthalazines with human liver enzyme has been studied using a spectrophotometric assay. Fifteen quinazoline and 14 phthalazine derivatives were found to be substrates for human liver aldehyde oxidase with Km values ranging from 5 to 500 microM. The substrate specificity of the quinazolines toward rabbit, guinea pig, and baboon liver aldehyde oxidase has also been investigated; the reaction of substituted phthalazines with mammalian liver enzyme has been reported previously (Beedham et al., 1990, Biochem. Pharmacol. 39, 1213-1221). Oxidation products of 2-substituted (4-substituted) quinazolines with rabbit liver aldehyde oxidase were identified by MS as 4-oxo (2-oxo)-quinazolines, respectively. In all cases, unsubstituted compounds gave the highest oxidation rates and the presence of lipophilic substituents presumably facilitated hydrophobic binding to the enzymes. However, there were marked differences in substrate specificity between human liver aldehyde oxidase and hepatic enzyme from rabbit, guinea pig, and baboon with the size of substrate being the differentiating factor. The molecular sizes of the substrates, estimated using calculated molar refractivities, ranked the size of the binding site of aldehyde oxidase in the order rabbit < guinea pig < baboon < man. Isoelectric points of the different aldehyde oxidase isozymes ranged from pH 5.10 for rabbit to 6.40 for the human liver isozyme. These results indicate that rabbit liver aldehyde oxidase shows marked differences from the human liver enzyme in its handling of quinazoline and phthalazine substrates.

Aldehyde Oxidase↗
PubMed2000

Lysyl oxidase and P-ATPase-7A expression during embryonic development in the rat.

Lysyl oxidase activity is critical for the assembly and cross-linking of extracellular matrix proteins, such as collagen and elastin. Moreover, lysyl oxidase activity is sensitive to changes in copper status and genetic perturbations in copper transport, e.g., mutations in the P-type ATPase gene, ATP7A, associated with cellular copper transport. Lysyl oxidase may also serve as a vehicle for copper transport from extracellular matrix cells. Herein, we demonstrate that sufficient lysyl oxidase functional activity is present in the rat embryo at gestation day (GD) 9 to be detected in conventional enzyme assays. Estimation of embryonic lysyl oxidase functional activity, however, required partial purification in order to remove inhibitors. From GD 9 to GD 15, lysyl oxidase activity was relatively constant when expressed per unit of protein or DNA. In contrast, the steady-state levels of lysyl oxidase and ATP7A mRNA, measured by RT-PCR and expressed relative to total RNA and cyclophilin mRNA, increased approximately fourfold from GD 9 to 15. The pattern of temporal expression for ATP7A was consistent with its possible role in copper delivery to lysyl oxidase.

Adenosine Triphosphatases↗
PubMed2002

The polyamine oxidase inactivator MDL 72527.

Polyamine oxidase is a FAD-dependent amine oxidase, which is constitutively expressed in nearly all tissues of the vertebrate organism. In 1985, N1,N4-bis(2,3-butadienyl)-1,4-butanediamine (MDL 72527) was designed as a selective enzyme-activated irreversible inhibitor of polyamine oxidase (EC 1.5.3.11). It inactivates, at micromolar concentration and time-dependently, the enzyme in cells, as well as in all organs of experimental animals, without inhibiting other enzymes of polyamine metabolism. MDL 72527 served during nearly two decades as a unique tool in the elucidation of the physiological roles of polyamine oxidase. The compound has anticancer and contragestational effects, and it improves the anticancer effect of the ornithine decarboxylase inactivator (D,L)-2-(difluoromethyl)ornithine (DFMO). Profound depletion of the polyamine pools of tumour cells and effects on different components of the immune defence system are responsible for the anticancer effects of MDL 72527/DFMO combinations. Recently a direct cytotoxic effect of MDL 72527 at concentrations above those required for polyamine oxidase inactivation was observed. The induction of apoptosis by MDL 72527 was ascribed to its lysosomotropic properties. Therapeutic potentials of the apoptotic effect of MDL 72527 need to be explored. Polyamine oxidase is the last enzyme of the polyamine interconversion pathway that awaits the detailed elucidation of its structure and regulation. MDL 72527 should be useful as a lead in the development of inactivators which are selective for the isoforms of polyamine oxidase. Isozyme-selective inhibitors will give more profound insights into and reveal a diversity of specific functions of polyamine oxidase.

Animals↗
PubMed1993

A soybean coproporphyrinogen oxidase gene is highly expressed in root nodules.

In plants the enzyme coproporphyrinogen oxidase catalyzes the oxidative decarboxylation of coproporphyrinogen III to protoporphyrinogen IX in the heme and chlorophyll biosynthesis pathway(s). We have isolated a soybean coproporphyrinogen oxidase cDNA from a cDNA library and determined the primary structure of the corresponding gene. The coproporphyrinogen oxidase gene encodes a polypeptide with a predicted molecular mass of 43 kDa. The derived amino acid sequence shows 50% similarity to the corresponding yeast amino acid sequence. The main difference is an extension of 67 amino acids at the N-terminus of the soybean polypeptide which may function as a transit peptide. A full-length coproporphyrinogen oxidase cDNA clone complements a yeast mutant deleted of the coproporphyrinogen oxidase gene, thus demonstrating the function of the soybean protein. The soybean coproporphyrinogen oxidase gene is highly expressed in nodules at the stage where several late nodulins including leghemoglobin appear. The coproporphyrinogen oxidase mRNA is also detectable in leaves but at a lower level than in nodules while no mRNA is detectable in roots. The high level of coproporphyrinogen oxidase mRNA in soybean nodules implies that the plant increases heme production in the nodules to meet the demand for additional heme required for hemoprotein formation.

Amino Acid Sequence↗
PubMed1992

Two independent mutational events in the loss of urate oxidase during hominoid evolution.

Urate oxidase was lost in hominoids during primate evolution. The mechanism and biological reason for this loss remain unknown. In an attempt to address these questions, we analyzed the sequence of urate oxidase genes from four species of hominoids: human (Homo sapiens), chimpanzee (Pan troglodytes), orangutan (Pongo pygmaeus), and gibbon (Hylobates). Two nonsense mutations at codon positions 33 and 187 and an aberrant splice site were found in the human gene. These three deleterious mutations were also identified in the chimpanzee. The nonsense mutation at codon 33 was observed in the orangutan urate oxidase gene. None of the three mutations was present in the gibbon; in contrast, a 13-bp deletion was identified that disrupted the gibbon urate oxidase reading frame. These results suggest that the loss of urate oxidase during the evolution of hominoids could be caused by two independent events after the divergence of the gibbon lineage; the nonsense mutation at codon position 33 resulted in the loss of urate oxidase activity in the human, chimpanzee, and orangutan, whereas the 13-bp deletion was responsible for the urate oxidase deficiency in the gibbon. Because the disruption of a functional gene by independent events in two different evolutionary lineages is unlikely to occur on a chance basis, our data favor the hypothesis that the loss of urate oxidase may have evolutionary advantages.

Amino Acid Sequence↗
PubMed1993

Induction of glucose oxidase, catalase, and lactonase in Aspergillus niger.

The induction of glucose oxidase, catalase, and lactonase activities was studied both in wild-type and in glucose oxidase regulatory and structural mutants of Aspergillus niger. The structural gene for glucose oxidase was isolated and used for Northern analysis and in transformation experiments using various gox mutations. Wild-type phenotype could be restored in the glucose oxidase-negative mutant (goxC) by transformation with the structural gene. We conclude, therefore, that the goxC marker which is located on chromosome 2 represents the structural gene of glucose oxidase. Glucose and a high oxygen level are necessary for the induction of all three enzyme activities in the wild-type strain and it was shown that both glucose and oxygen effects reflect regulation at the transcriptional level. The goxB mutation results in constitutive expression of all three activities although modulated to some extent by the carbon source. The goxE mutation only has an effect on lactonase and glucose oxidase expression and does not relieve the necessity for a high oxygen level. Catalase and lactonase could not be induced in the glucose oxidase-negative strain (goxC). Addition of H2O2 resulted in the induction of all three enzymes in the wild-type without glucose being present. The H2O2 induction is probably mediated by the goxB product. Besides the H2O2 induction there is still an effect of the carbon source on the induction. A model for induction of glucose oxidase, catalase, and lactonase in A. niger is discussed.(ABSTRACT TRUNCATED AT 250 WORDS)

Aspergillus↗
PubMed1995

Activity measurements of acyl-CoA oxidases in human liver.

Peroxisomal beta-oxidation is involved in the degradation of different fatty acids or fatty acid derivatives including eicosanoids (prostaglandins, leukotrienes, thromboxanes), dicarboxylic fatty acids, very long-chain fatty acids, pristanic acid, bile acid intermediates (di- and trihydroxycoprostanoic acids), and xenobiotics. Separate beta-oxidation systems are probably active inside peroxisomes, each acting on a distinct set of substrates, as suggested by the discovery of multiple acyl-CoA oxidases. Using specific substrates or selective conditions, we can distinguish in rat liver the action of acyl-CoA oxidases (type I and II), a pristanoyl-CoA oxidase and a trihydroxycoprostanoyl-CoA oxidase, and, in in human liver, of acyl-CoA oxidase (type I and II) and a branched-chain acyl-CoA oxidase. When incubated with suitable CoA-esters, these different oxidases can be measured in a similar fashion by following fluorimetrically the dimerization of homovanillic acid, catalysed by peroxidase in the presence of hydrogen peroxide. The optimal assay conditions and possible pitfalls in this type of coupled assay are discussed. This knowledge can be used to reveal the existence of peroxisomal disorders in which only one acyl-CoA oxidase is deficient.

Acyl-CoA Oxidase↗
PubMed1988

Histochemical localisation of monoamine oxidase A and B in rat brain.

The histochemical distribution of monoamine oxidase A and B in rat brain was investigated using a coupled peroxidatic technique with benzylamine and tyramine as substrates and clorgyline and (-)-deprenyl as selective inhibitors. Benzylamine oxidase was absent in all areas. Both forms of monoamine oxidase were present, at low levels, in all areas; in addition several regions showed high activity of one or other form or both. Substantial activity of monoamine oxidase B was identified in the pineal gland, the lining of the ventricles, several hypothalamic regions, and the raphe nuclei. The locus coeruleus and interpeduncular nucleus possessed considerable type A activity. The substantia nigra and striatum showed no staining above the low general level, although the ventral tegmental area showed higher levels of both A and B. In general, noradrenaline-containing neuronal cell body areas showed monoamine oxidase A, and 5-hydroxytryptamine-rich areas monoamine oxidase B. There was no consistent enrichment of either in corresponding dopamine-rich regions. Monoamine oxidase thus appears to have a different role in these three types of neuron. The low level of monoamine oxidase B in the nigrostriatal tract may help to explain the resistance of the rat to MPTP toxicity.

Animals↗
PubMed1981

Properties of two urate oxidases modified by the covalent attachment of poly(ethylene glycol).

Poly(ethylene glycol) of 5 000 daltons has been attached covalently to preparations of urate oxidase (urate: oxygen oxidoreductase, EC 1.7.3.3) from hog liver and Candida utilis. Attachment of sufficient poly(ethylene glycol) to either urate oxidase renders the enzyme incapable of eliciting antibody production in mice, or of reacting with antibodies to the unmodified enzyme. The poly(ethylene glycol) : urate oxidase conjugates exhibit higher Km and lower V values than the unmodified urate oxidases. Optimal pH values are increased for the poly(ethylene glycol) : urate oxidases, and optimal temperatures are decreased. The blood circulating lives of the modified urate oxidases following intravenous injection are much longer than those of the unmodified urate oxidases: repetitive injections over a period of 90 days dd not alter the blood circulating lives of the poly(ethylene glycol) : urate oxidases. The unmodified enzymes, on the other hand, were cleared from the blood with extreme rapidity after a few intravenous injections.

Animals↗
PubMed1987

The effects of reversible freezing inactivation and inhibitor binding on redox properties of L-amino-acid oxidase.

We measured the redox potentials of frozen inactivated L-amino-acid oxidase (L-amino-acid:oxygen oxidoreductase (deaminating), EC 1.4.3.2) and inhibitor-bound (anthranilic acid) enzyme, and compared these redox properties to those of active L-amino-acid oxidase and benzoate-bound D-amino-acid oxidase (EC 1.4.3.3), respectively. The redox properties of the inactive enzyme are similar to the properties of free flavin; the potential is within 0.015 V of free flavin and no radical stabilization is seen. This corresponds to the loss of most interactions between apoprotein and flavin. In contrast, the anthranilic acid lowers the amount of radical stabilized from 85% to 35%. The potentials are still 0.150 V positive of free flavin, indicating that in the presence of inhibitor, many flavin-protein interactions remain intact. The difference between this behavior and that of D-amino-acid oxidase bound to benzoate, where the amount of radical declined from 95% to 5%, is explained on the basis of the relative tightness of binding of apoprotein to FAD. D-Amino-acid oxidase apoprotein has a relatively low Ka (10(6)) for FAD, and benzoate has a relatively high Ka (10(5)) for the enzyme. Therefore, the binding of benzoate increases the tightness of FAD binding to apo-D-amino-acid oxidase (10(11)), indicating significant changes in flavin-protein interactions. In contrast, apo-L-amino-acid oxidase binds flavin tightly (the Ka is greater than 10(7)) and the enzyme binds to anthranilate much less tightly, with a Ka of 10(3). The L-amino-acid oxidase apoprotein binding to FAD is tight initially, and the binding of anthranilate changes it only slightly.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Oxidoreductases↗
PubMed1979

Degradation of peroxisomal catalase and urate oxidase of rat liver.

Urate oxidase and catalase were purified from rat liver peroxisomes, and respective antibodies were prepared from rabbits by the administration of these enzymes. Although urate oxidase generally precipitates in immunoprecipitation-possible pH ranges (pH 4.5--9.5), the enzyme remained soluble in 50 mM glycine buffer (pH 9.5) containing 50% glycerol up to concentration of 0.3 mg/ml. Anti-urate oxidase reacted with purified urate oxidase as well as with the crude preparation. After [3H]leucine was injected to rats, urate oxidase and catalase were purified from rat liver at certain intervals, and further precipitated by respective antibodies. The half-life of the catalase was 39 h and that of urate oxidase, 20 h. When the sonicated light mitochondrial fraction was incubated at 37 degrees C and at pH 7.0 or 5.6, inactivation of catalase did not seem to differ between these pH values, and approximately 80% of the catalase activity remained even after 8 h. Urate oxidase was inactivated very rapidly at pH 5.6; only 30% of its activity survived incubation for 6 h. This inactivation was found to occur by some proteolytic process. From these findings, the turnover rate of urate oxidase was found to be different from that of catalase, and this distinction seemed to be due to different sensitivity to some degradative enzymes.

Animals↗
PubMed1982

Induction of diamine oxidase activity in rat kidney during compensatory hypertrophy.

Diamine oxidase (EC 1.4.3.6) activity, measured as [14C]delta1 -pyrroline formation from [14C]putrescine, was studied in homogenates of rat kidney during compensatory hypertrophy after unilateral nephrectomy. Acetaldehyde and to a lesser degree phenobarbital, at concentrations which did not modify the activity of a preparation of hog kidney diamine oxidase, increased delta1 -pyrroline formation in kidney homogenate, which suggests that aldehyde-metabolizing enzymes present in this tissue may interfere with the yield of delta1 -pyrroline formation and that the use of acetaldehyde may give better information on kidney diamine oxidase activity. Other inhibitors of aldehyde-metabolizing enzymes such as chloral hydrate, disulfiram, and pyrazole cannot be used for diamine oxidase determination since they stimulated or depressed this enzyme activity. In rat kidney undergoing compensatory hypertrophy the levels of putrescine, spermidine, and spermine increased rapidly and were followed by an increase in diamine oxidase activity that presented a first peak on day 2 and a second peak on day 6. The administration of cycloheximide or actinomycin D to nephrectomized rates prevented the increase in diamine oxidase activity. The study of the turnover rate of diamine oxidase with cycloheximide demonstrated that the half-life of this enzyme was about 14 h in normal and hypertrophic kidney. The results suggest that the increase in diamine oxidase activity in renal hypertrophy was due to the synthesis of new enzymes rather than to slowing of its degradation.

Acetaldehyde↗