Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:1.11.1.7 (peroxidase)
 65,474 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Tyrosine hydroxylase, dopa oxidase, and peroxidase activities were studied in soluble fractions of B16 melanoma tumor homogenates by polyacrylamide gel disc electrophoresis. Stained gels were scanned photometrically and gel slices were assayed radiometrically. In these preparations, the two bands of tyrosine hydroxylating activity were completely separated from the peroxidase activity but coincided with two major bands of dopa oxidase activity. The third dopa oxidase band coincided with the single band of peroxidase activity. The soluble fraction of cultured cell homogenates had no peroxidase activity, but the two tyrosine hydroxylase bands coincided exactly with the two dopa oxidase bands. Therefore, in the soluble fraction of the murine melanoma bifunctional tyrosinase does exist as two electrophoretically separable forms which are independent of peroxidase.
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PMID:Characteristics of tyrosinase in B16 melanoma. 1 62

Substituted primary hydroxamic acids were found to inhibit the catalytic activity of a number of redox enzymes. The inhibition was not related to the nature of the metal-active site of the enzyme nor to the nature of the oxygen-containing substrate. Two easily available enzymes, mushroom tyrosinase (monophenol,dihydroyphenylalanine:oxygen oxidoreductase, EC 1.14.18.1) and horseradish peroxidase (donor:hydrogen-peroxide oxidoreductase, EC 1.11.1.7), which were potently inhibited by hydroxamic acids, were chosen for more detailed study. A kinetic analysis of the inhibitory effects on the partially purified tyrosinase of mushroom (Agaricus bispora) revealed that inhibition was reversible and competiitive with respect to reducing substrate concentration, but was not competitive with respect to molecular oxygen concentration. A spectrophotometric and EPR study of the binding of salicylhydroxamic acid to horseradish peroxidase revealed that his hydroxamic acid was bound to the enzyme in the same manner as a typical substrate, hydroquinone. Spectroscopic and thermodynamic measurements of the binding reactions suggested that this binding site is close, to but, not directly onto, the heme group of the enzyme. From these results it is concluded that the mode of inhibition of hydroxamic acid need not be, as generally supposed, by metal chelation, and mechanisms involving either hydrogen bonding at the reducing substrate binding site or the formation of a charge transfer complex between hydroxamic acid and an electron-accepting group in the enzyme are considered to be more feasible. The relevance of these findings to deductions on the nature of other hydroxamic acid-inhibitable systems is discussed.
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PMID:Studies on the mechanism of inhibition of redox enzymes by substituted hydroxamic acids. 21 Aug 15

A number of enzymes, presumably secreted by larvae of B. microplus under natural feeding conditions, have been investigated in the skin of previously unexposed calves 4 h after infestation at the attachment site. Carboxylic ester hydrolase activity was demonstrated in the dermis, immediately adjacent to the mouthparts, or in the attachment cone, depending on substrate and reaction pH. The carboxylic ester hydrolase acting on naphthol AS-D acetate (2-acetoxy-3-naphthoic-O-toluidide) at pH 7-1 was characteristically found in the dermis and not in the attachment cone. The use of specific inhibitors showed that this enzyme was primarily a B-esterase or carboxylesterase with possibly a small portion of C-esterase or acetylesterase. It is postulated that carboxylic ester hydrolase could contribute to the dilation observed in the subepidermal capillaries adjacent to the attachment sites of unexposed animals, through the formation of plasma kinins. Other enzymes demonstrated in the dermis, adjacent to the mouthparts, were triacylglycerol lipase, as an aggregated deposit, and small amounts of aminopeptidase (microsomal) and monophenol monooxygenase. Aminopeptidase (microsomal) was also demonstrated in the attachment cone or adjacent epidermis, according to the substrate used. No activity was found in the host tissue, in association with the attachment site, for either alkaline or acid phosphatase, acetylcholinesterase or cholinesterase, peroxidase or amine oxidase (flavin-containing), despite the intense histochemical reaction for the latter in the tissues of larvae.
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PMID:Boophilus microplus: characterization of enzymes introduced into the host. 102 62

Tubers of potato (Solanum tuberosum L.) contain a number of chitin-binding proteins which have possible functions in defence against pathogens. A major protein of the tuber is the chitin-binding lectin which has been further characterized with respect to its antigenicity and N-terminal amino acid sequence. By using an antiserum monospecific for tuber lectin in unwounded potato the protein was found in the cytoplasm and vacuole, unusually for a hydroxyproline-rich glycoprotein, but consistent with its soluble nature in subcellular extracts. Little increased synthesis of the lectin precursor or the post-translationally modified form could be demonstrated in excised potato tuber discs. However, after wounding there is increased synthesis of another hydroxyproline-containing glycoprotein of Mr 57,000, which binds to chitin and shares common epitopes with the lectin. In comparison with the tuber lectin, this novel glycoprotein contains less hydroxyproline, but from its overall composition it is clearly not an underhydroxylated form of the tuber lectin. It differed in its N-terminal amino acid sequence and was much less glycosylated, although arabinose was still present. Synthesis of the Mr-57,000 polypeptide began after the initial burst of protein synthesis and increased, reaching a peak at 24 h after wounding. The protein was produced with its enzymes of post-translational modification, prolyl hydroxylase and arabinosyltransferase, concomitantly with the marker enzymes for wounding, phenylalanine ammonia-lyase and membrane-bound phenol oxidase and peroxidase.
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PMID:Chitin-binding proteins in potato (Solanum tuberosum L.) tuber. Characterization, immunolocalization and effects of wounding. 159 Jul 71

Tyrosinase (EC 1.14.18.1)/O2, ceruloplasmin (human type X)/O2, and peroxidase (EC 1.11.1.7)/H2O2 oxidized the endogenous central nervous system alkaloid salsolinol (SAL) at physiological pH. The proximate oxidation product was an electrophilic ortho-quinone (4) which at pH 7.0 rapidly tautomerized. Four major initial products were formed from 4: cis- and trans-1,2,3,4-tetrahydro-1-methyl-4,6,7-isoquinolinetriol (A and B, respectively), 2,3,4-trihydro-1-methyl-7-hydroxy-6-oxyisoquinoline (C), and 1-methyl-6,7-isoquinoline diol (D). Mechanisms describing the formation of these products have been presented. Ortho-quinone 4, formed in the enzyme-mediated reactions, was rapidly attacked by glutathione to yield the 5-S-, 8-S-, and 5,8-bi-S-glutathionyl conjugates of SAL. Preliminary experiments indicated that injection of A, B and C into the CNS of mice evoked profound behavioral effects. Quinone methide C was toxic. The potential role of the oxidation of salsolinol in the neurodegenerative and behavioral effects associated with chronic alcoholism is discussed.
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PMID:Interactions of salsolinol with oxidative enzymes. 165 22

A novel peroxidase that catalyses the dimerization of ferulic acid or caffeic acid via oxidative coupling and formation of beta beta'-linkage to the lignan-type compounds 8,8'-bis(caffeic acid) or 8,8'-bis(ferulic acid) respectively was purified from the leaves of Bupleurum salicifolium. The enzyme, for which the name caffeate peroxidase is proposed, was purified 2700-fold. It is a glycoprotein and has an Mr of 38,000 as determined by gel filtration and SDS/PAGE. The Km values for ferulic acid and caffeic acid were 0.24 mM and for H2O2 0.04 mM with caffeic acid and 0.48 mM with ferulic acid. The purified peroxidase does not exhibit activity on other phenylpropanoids tested and has no detectable phenol oxidase or NADPH oxidase activity. The caffeate peroxidase could be involved in the biosynthesis of lignans.
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PMID:Purification of a new peroxidase catalysing the formation of lignan-type compounds. 184 25

Peroxidase (EC 1.11.1.7)/H2O2, ceruloplasmin (human type X)/O2, and tyrosinase (EC 1.14.18.1)/O2 all oxidized the indolic neurotransmitter 5-hydroxytryptamine (5-HT) in the physiological pH domain. Peroxidase/H2O2 oxidized 5-HT at pH values down to about 2.5. All oxidation reactions generated complex mixtures of products which included at least one known neurotoxin, tryptamine-4,5-dione. In general, the enzymatic oxidation pathways paralleled the in vitro electrochemical oxidation of 5-HT which has permitted suggestions to be made concerning the probable mechanisms of the enzyme-mediated reactions.
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PMID:Interactions of 5-hydroxytryptamine with oxidative enzymes. 190 Dec 10

The early enzyme-mediated reaction sequence in the biosynthesis of melanin from L-tyrosine involves an initial hydroxylation (monophenol oxidase activity, MPO) of the aromatic amino acid precursor to form L-dopa (3,4-dihydroxyphenylalanine), and the ensuing oxidation (diphenol oxidase activity, DPO) of the resultant diphenol to form dopaquinone. By means of high pressure liquid chromatography with electrochemical detection (HPLC-ED) both phenol oxidase activities were observed in the blood (hemolymph) of two species of insect, third-stage larvae of Drosophila melanogaster and adult Locusta migratoria, and in an adult fresh-water crayfish, Austropotamobius pallipes. These results establish that in each species MPO and DPO can be detected readily without the use of exogenous activators.
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PMID:Hemolymph phenol oxidases in Drosophila melanogaster, Locusta migratoria, and Austropotamobius pallipes. 195 49

Tyrosinase usually catalyzes the conversion of monophenols to o-diphenols and oxidation of diphenols to the corresponding quinones. However, when 3,4-dihydroxymandelic acid was provided as the substrate, it catalyzed an unusual oxidative decarboxylation reaction generating 3,4-dihydroxybenzaldehyde as the sole product. The identity of the product was confirmed by high-performance liquid chromatography (HPLC) as well as ultraviolet and infrared spectral studies. None of the following enzymes tested catalyzed the new reaction: galactose oxidase, ceruloplasmin, superoxide dismutase, ascorbate oxidase, dopamine beta-hydroxylase, and peroxidase. Phenol oxidase inhibitors such as phenylthiourea, potassium cyanide, and sodium azide inhibited the reaction drastically, suggesting the participation of the active site copper of the enzyme in the catalysis. Mimosine, a well-known competitive inhibitor of tyrosinase, competitively inhibited the new reaction also. 4-Hydroxymandelic acid and 3-methoxy-4-hydroxymandelic acid neither served as substrates nor inhibited the reaction. Putative intermediates such as 3,4-dihydroxybenzyl alcohol and (3,4-dihydroxybenzoyl)formic acid did not accumulate during the reaction. Oxidation to a quinone methide derivative rather than conventional quinone accounts for this unusual oxidative decarboxylation reaction. Earlier from this laboratory, we reported the conversion of 4-alkylcatechols to quinone methides catalyzed by a cuticular phenol oxidase [Sugumaran, M., & Lipke, H. (1983) FEBS Lett. 155, 65-68]. Present studies demonstrate that mushroom tyrosinase will also catalyze quinone methide production with the same active site copper if a suitable substrate such as 3,4-dihydroxymandelic acid is provided.
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PMID:Tyrosinase catalyzes an unusual oxidative decarboxylation of 3,4-dihydroxymandelate. 309 74

Acanthamoeba castellanii has a phenol oxidase activity that is believed to be a laccase. Enzyme activity was found in the outer cyst wall, in the cytoplasm of encysting amoebae and in the encystment medium. Encystment procedures were modified to promote an increase in the amount of soluble enzyme secreted during encystation. Acanthamoeba polyphenol oxidase has a pH optimum of 6.0 and a Km value of 0.21 mM with dihydroxyphenylalanine. The enzyme does not oxidize tyrosine, and it is inhibited by chloride but not by inhibitors of peroxidase. Its synthesis coincides with encystation, and known inhibitors of polyphenol oxidase prevent encystation. Polyphenol oxidase may have a role in making the cyst resistant to mechanical and chemical breakdown.
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PMID:Polyphenol oxidase produced during encystation of Acanthamoeba castellanii. 393 Jul 6


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