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PubMed1983

A yeast mitochondrial inner membrane 30K hydrophobic protein: comparison with subunit 32K of the cytochrome BC 1 complex.

A yeast mitochondrial inner membrane hydrophobic protein 30K has been isolated and compared to subunit 32K of the yeast cytochrome bc 1 complex. Both proteins are translated on mitochondrial ribosomes, have nearly the same molecular weight and similar aminoacid compositions. Comparison was carried out by immunological techniques with specific antibodies, and by studying 3 yeast strains having mutations in the COB region of the mitochondrial DNA. Results show that the two proteins are not identical.

Electron Transport Complex III↗

PubMed1989

L-pipecolate oxidase: a distinct peroxisomal enzyme in man.

We investigated the oxidation of L-pipecolate in human liver. The results obtained with L-pipecolate from which traces of D-pipecolate had been removed by a preincubation with D-aminoacid oxidase indicate that a distinct L-pipecolate oxidase rather than D-aminoacid oxidase is responsible for the L-pipecolate dependent H2O2-production in human liver. Importantly, L-pipecolate oxidase was found to be localized in peroxisomes which adds to the growing number of enzymes and metabolic functions which can be ascribed to peroxisomes.

Animals↗

PubMed1982

[Cold adaptation and changes in peroxisome enzyme in various organs of the rat].

In the rat brown fat peroxisomes - thermogenetic organules - an peroxisomal enzyme activities undergo remarkable changes during the adaptation to cold of the animals (see 3). In this paper was show that changes of peroxisomal enzyme activities occur also in liver and kidney during cold-adaptation. Catalase, L-hydroxyacid oxidase, uricase and D-aminoacid oxidase (DAO) were assayed as in (6). During cold-adaptation, the activity of the former three enzymes (Table 2) increases with the weight of the organs (Table 1) whereas that of DAO exhibits a much larger increase (Table 3). Results are discussed with regard to the contribution of the liver to non-shivering thermogenesis.

Adaptation, Physiological↗

PubMed1992

Enzymatic method for phenylketonuria screening using phenylalanine dehydrogenase.

An enzymatic method using phenylalanine dehydrogenase (PheDH;EC 1.4.1.-) for the determination of phenylalanine in blood-spot specimens has been developed for the Cobas Bio centrifugal analyser. Method accuracy was established by correlation of results from blood spots with phenylalanine values obtained by quantitative aminoacid analysis on simultaneously collected plasma specimens. The phenylalanine dehydrogenase method demonstrated linearity to 2500 mumol/L and had recoveries of 89.4 +/- 4.6% (mean +/- SEM). The between-run precision using blood-spot specimens was 9.8% at 285 mumol/L. In the context of a routine newborn screening program, the enzymatic method was found to have a lower false-positive rate (1% vs 3%) when evaluated against the classical fluorimetric Autoanalyser method.

Amino Acid Oxidoreductases↗

PubMedDate not supplied

Purification and characterization of hepatic P-450IIE1 from acetone-treated mice.

A new cytochrome P-450 isozyme (Mr = 52,000) was purified to apparent electrophoretic homogeneity from hepatic microsomes of mice treated with acetone and its biochemical, spectral, and immunological properties characterized. Several criteria indicated that the purified cytochrome was distinct from the known mouse P-450 isozymes. The absolute spectrum of its oxidized form indicated that it was in the high spin state. In a reconstituted system, it showed low catalytic activities towards 7-ethoxycoumarin, aminopyrine, and coumarin, whereas it catalyzed the oxidation of aniline, acetone, dimethylnitrosamine with high turnover number. The mouse enzyme was immunoreactive with polyclonal antibodies against rat P-450IIE1 and exhibited an NH2-terminal aminoacid sequence with a high homology to that of rat-P-450IIE1. Based upon the above catalytic, spectral, immunological and structural properties, the purified mouse P-450 appears to be the ortholog of previously described P-450IIE1(s) of other species.

Acetone↗

PubMedDate not supplied

Oxidative deamination of S-(1-carboxyethyl)-L-cysteine and S-(1-carboxypropyl)-L-cysteine by L-aminoacid oxidase.

S-(1-carboxyethyl)-L-cysteine (1-CEC) and S-(1-carboxypropyl)-L-cysteine (1-CPC) are oxidatively deaminated by L-aminoacid oxidase with consumption of half a mole of oxygen per mole of substrate in the presence of catalase. This reaction gives rise to the corresponding alpha-ketoacids, identified by some chemical and chromatographic tests and by comparison with synthetic compounds. It has been possible, therefore, to demonstrate that S-(1-carboxyethyl)-thiopvruvic acid (1-CETP) and S-(1-carboxypropyl)-thiopvruvic acid (1-CPTP) are the main products of oxidative deamination of 1-CEC and 1-CPC.

Amino Acid Oxidoreductases↗

PubMed1985

alpha-Ketoacid dehydrogenase complexes and respiratory fuel utilisation in diabetes.

Activity of the pyruvate dehydrogenase complex determines the rate of glucose oxidation in animals including man. The complex is regulated by reversible phosphorylation, phosphorylation resulting in inactivation. Activity is therefore dependent upon the activities of pyruvate dehydrogenase kinase and phosphatase. Activity of the complex is reduced in diabetes and starvation as a result of insulin deficiency. The mechanism involves activation of pyruvate dehydrogenase kinase by short-term effects of products of fatty acid oxidation and by longer term effects involving specific protein synthesis; in hepatocytes the signals may include lipid fuels and glucagon. Activity of the branched chain ketoacid dehydrogenase complex determines the rate of degradation of branched chain aminoacids which is adjusted according to dietary supply. The complex is regulated by reversible phosphorylation, phosphorylation being inactivating. In liver and kidney, but not in muscles a protein activator (free E1 component) may reactivate phosphorylated complex without dephosphorylation and facilitate hepatic oxidation of branched chain ketoacids. Metabolic adjustments induced by diet and diabetes include loss of activator protein, loss of total complex activity in liver but not muscles, and enhanced inactivation by phosphorylation in liver.

3-Methyl-2-Oxobutanoate Dehydrogenase (Lipoamide)↗

PubMed1998

Destruction of catecholamine-containing neurons by 6-hydroxydopa, an endogenous amine oxidase cofactor.

The amino acid, 6-hydroxydopa (6-OHDOPA), found at the active site of amine oxidases, exists as a keto-enol. Exogenously administered 6-OHDOPA is an excitotoxin like beta-N-oxalylamino-L-alanine (BOAA) and beta-N-methylamino-L-alanine (BMAA), acting at the non-N-methyl-D-aspartate (non-NMDA) alpha-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid (AMPA) receptor. BMAA and BOAA are causal factors of neurolathyrism in humans. Much exogenously administered 6-OHDOPA is biotransformed by aminoacid decarboxylase (AADC) to the highly potent and catecholamine-(CA) selective neurotoxin, 6-hydroxydopamine (6-OHDA). 6-OHDOPA destroys locus coeruleus noradrenergic perikarya and produces associated denervation of brain by norepinephrine-(NE) containing fibers. Opiopeptides and opioids enhance neurotoxic effects of 6-OHDOPA on noradrenergic nerves, by a naloxone-reversible process. An understanding of mechanisms underlying neurotoxic effects of 6-OHDOPA can be helpful in defining actions of known and newfound amino acids and for investigating their potential neurotoxic properties.

Amine Oxidase (Copper-Containing)↗

PubMed1976

Cytochemical studies on the localization of methanol oxidase and other oxidases in peroxisomes of methanol-grown Hansenula polymorpha.

The localization of methanol oxidase activity in cells of methanol-limited chemostat cultures of the yeast Hansenula polymorpha has been studied with different cytochemical staining techniques. The methods were based on enzymatic or chemical trapping of the hydrogen peroxide produced by the enzyme during aerobic incubations of whole cells in methanol-containing media. The results showed that methanol-dependent hydrogen peroxide production in either fixed or unfixed cells exclusively occurred in peroxisomes, which characteristically develop during growth of this yeast on methanol. Apart from methanol oxidase and catalase, the typical peroxisomal enzymes D-aminoacid oxidase and L-alpha-hydroxyacid oxidase were also found to be located in the peroxisomes. Urate oxidase was not detected in these organelles. Phase-contrast microscopy of living cells revealed the occurrence of peroxisomes which were cubic of form. This unusual shape was also observed in thin sections examined by electron microscopy. The contents of the peroxisomes showed, after various fixation procedures, a completely crystalline or striated substructure. It is suggested that this substructure might represent the in vivo organization structure of the peroxisomal enzymes.

Alcohol Oxidoreductases↗

PubMedDate not supplied

Oxidative deamination of epsilon-N-acetylthialysine and epsilon-N-acetylselenalysine by snake venom L-aminoacid oxidase.

epsilon-N-acetylthialysine and epsilon-N-acetylselenalysine are oxidatively deaminated by Crotalus adamanteus l-aminoacid oxidase, giving rise to the corresponding alpha-ketoacids, identified by some chemical and chromatographic tests and by comparison with synthetic compounds. no cleavage of the C-S or C-Se bonds of the substrates occurs during the reaction. The enzyme acts as well on the epsilon-N-acetylderivatives of thialysine and selenalysine as on epsilon-N-acetyllysine. The substitution of the gamma methylene group of lysine by a sulfur or a selenium atom seems not to greatly affect the substrate specificity of the enzyme.

Amino Acid Oxidoreductases↗

PubMed1984

Activity of peroxisomal enzymes and intracellular distribution of catalase in Zellweger syndrome.

The activity of peroxisomal enzymes was studied in human liver and cultured human skin fibroblasts in relation to the finding (Goldfischer, S. et al. (1973) Science 182, 62-64) that morphologically distinct peroxisomes are not detectable in patients with the cerebro-hepato-renal (Zellweger) syndrome. In homogenates of liver from the patients, dihydroxyacetone phosphate acyltransferase, a membrane-bound peroxisomal enzyme, is deficient (Schutgens, R.B.H., et al. (1984) Biochem. Biophys. Res. Commun. 120, 179-184). In contrast, there is no deficiency of the soluble peroxisomal matrix enzymes catalase, L-alpha-hydroxyacid oxidase and E-aminoacid oxidase. Catalase is also not deficient in homogenates of cultured skin fibroblasts from the patients. The results of digitonin titration experiments showed that in control fibroblasts at least 70% of the catalase activity is present in subcellular particles distinct from mitochondria or lysosomes. In contrast, all of the catalase activity in fibroblasts from Zellweger patients is found in the same compartment as the cytosolic marker enzyme lactate dehydrogenase.

Acyltransferases↗

PubMed1982

Evidence for different localization of glutathione oxidase and gamma-glutamyltransferase activities during extracellular glutathione metabolism in isolated perfused rat kidney.

The metabolism of extracellular glutathione was studied in the isolated, perfused rat kidney. The results indicate different localization of glutathione oxidase and gamma -glutamyltransferase (5-glutamyl)-peptide: aminoacid 5-glutamyltransferase, EC 2.3.2.2) activities, since glutathione oxidase activity was observed only with glutathione present in the perfusate, whereas gamma -glutamyltransferase-mediated metabolism of glutathione was restricted to glutathione present to the localization of renal gamma -glutamyltransferase in the brush border membranes of the tubular epithelium, but suggest an opposite localization of renal glutathione oxidase activity, i.e., in the basal plasma membrane fraction of the tubular cells, facing the capillary bloodstream. Furthermore, the existence of the tubular glutathione extraction mechanism operating in addition to glomerular filtration is confirmed.

Animals↗

PubMed2002

Biosensor for the enantioselective analysis of the thyroid hormones (+)-3,3',5-triiodo-L-thyronine (T3) and (+)-3,3',5,5'-tetraiodo-L-thyronine (T4).

An amperometric biosensor based on L-aminoacid oxidase is proposed for enantioselective assay of (+)-3,3',5-triiodo-L-thyronine (L-T3) and (+)-3,3',5,5'-tetraiodo-L-thyronine (L-T4), due to the fact that only the L enantiomer has the hormonal activity. The construction of the amperometric biosensor is simple and reproducible. The analytical information obtained from enantioselective analysis are reliable. The RSD <1% assured by using the amperometric biosensors for L enantiomers assay as raw materials, and from tablets, demonstrated their suitability for the analysis of T3 and T4 at ppb concentration levels.

Amino Acid Oxidoreductases↗

PubMed1982

Peroxisomal enzyme activities in regenerating liver of rats.

The activities of five peroxisomal enzymes (fatty acyl-CoA oxidase, FAO; uricase, U; L-hydroxyacid oxidase, LHAO; D-aminoacid oxidase, DAO; and catalase, C and the triglyceride content were determined in the regenerating liver of rats after partial hepatectomy. The FAO activity was significantly increased on day 3. Thus, its rise followed the increase of the triglyceride content and preceded the disappearance of steatosis. For U and LHAO a similar progressive increase in activities was obtained on days 3, 5, and 7 of regeneration. DAO exhibited a highly significant increase on day 1. C increased on day 1 and then again after day 3. It is concluded that peroxisomal functions are not restored at parallel rates during liver regeneration.

Acyl-CoA Oxidase↗

PubMed1992

Peroxisomes in human colon carcinomas. A cytochemical and biochemical study.

The presence of peroxisomes and their enzymic content were investigated and compared in healthy and neoplastic human colon epithelial cells using cytochemical studies at the ultrastructural level as well as biochemical analyses. Catalase-positive organelles were found to be more numerous in normal than in colonic neoplastic cells. Biochemical assays revealed that no D-aminoacid oxidase or L-alpha-hydroxyacid oxidase activity was detected in normal or tumor tissues. The specific activities of catalase, fatty-acyl CoA oxidase and enoyl-CoA hydratase/3 hydroxyacyl-CoA dehydrogenase (the so-called peroxisomal bifunctional enzyme of the beta-oxidation system) were found to be diminished in carcinoma cells compared with the control tissue. The fall in catalase activity correlated well with tumor stage according to Dukes, suggesting that this peroxisomal enzyme could be used as a potential prognostic marker.

3-Hydroxyacyl CoA Dehydrogenases↗

PubMed1976

Oxidation of S-e-carboxymethyl-selenocysteine by L-aminoacid oxidase and by D-aspartate oxidase.

Se-Carboxymethyl-DL-selnocysteine (CMSeC) has been prepared in a pure crystalline form from selenocysteine and monochloracetic acid. It has been shown that CMSeC is a substrate for the L-aminoacid oxidase form snake venom and for the D-aspartate oxidase from beef kidney. Oxygen consumption and ammonia production indicate that only the L or the D form of CMSeC ar acted upon respectively by one or the other of the above enzymes. No noticeable differences were shown in the oxidation rate of CMSeC and S-carboxymethylcysteine, an indication that the substitution of a selenium for a sulfur atom in the molecule does not greatly affect the substrate specificity of the two enzymes. Data have been obtained suggesting that the product of the oxidative deamination of CMSeC Is Se-carboxymethyl-selenopyruvic acid.

Amino Acid Oxidoreductases↗

PubMed1975

Errors in metabolic regulation. A common group of metabolic disorders.

It is postulated that errors in metabolic regulation occur when aminoacid subsitutions or conformational changes occur at allosteric sites on proteins. The cell thus contains its full complement of enzymes, carrier proteins, and receptors, but these proteins do not respond normally to microenvironmental agents such as hormones or activator or inhibitor metabolites. Regulatory errors differ from the classical inborn errors in a number of respects: they can be acquired as well as inherited, when due to defects at allosteric inhibitory sites they lead to loss of regulation of metabolic pathways with oversynthesis of metabolic products without gross accumulation of abnormal intermediates, and they can be treated, in principle, by enzyme inhibitors rather than by enzyme replacement, as for inborn errors.

Adipose Tissue↗

PubMed1976

Enzymic and morphological studies on catalase positive particles from brown fat of cold adapted rats.

Brown adipose tissue of normal and cold-adapted adult rats has been investigated morphologically and cytochemically. In thin-sections catalase-positive particles appear as circular, oval or elongated profiles lying either as single particles or forming groups. Biochemical studies on peroxisomal enzymes show an increase of catalase activity to the tenfold amount after cold adaptation. The tissue is devoid of D-aminoacid oxidase and glycolate oxidase, while low activities of middle-chain-alpha-hydroxyacid oxidases could be detected. The catalase-positive particles were purified by differential and is lower than that of the liver peroxisomes. Enzymic investigations of the fractions render it probably that particles contain carnitine acetyltransferase, whereas they are lacking NAD-dependent glycerophosphate dehydrogenase. The pellets derived from the gradient centrifugation have been checked morphologically for purity. After performing DAB-cytochemistry for identification of the peroxidatic activity of catalase, most of the particles were shown to be structurally intact and homogeneously filled with reaction product.

Adipose Tissue, Brown↗