Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:1.10.3.3 (ascorbate oxidase)
 778 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Since cytochrome c and acetylated cytochrome c disappear from the circulation with a half-life of 4 min, these proteins cannot be used for in vivo detection of superoxide radicals and related metabolites. To determine superoxide and other radicals in vivo, a cytochrome c derivative (SMAC) was synthesized by linking 1 mol of poly(styrene-co-maleic acid) butyl ester (SM) to cytochrome c, followed by acetylation of its lysyl amino groups. SMAC retained 8 and 80% of cytochrome c activity to react with ascorbyl and superoxide radicals, respectively. However, SMAC did not serve as a substrate for cytochrome c reductase and cytochrome c oxidase. When injected intravenously to the rat, SMAC circulated bound to albumin with a half-life of 130 min. SMAC was rapidly reduced in the circulation of intact animals. Treatment of animals with paraquat markedly enhanced the reduction of the circulating SMAC. We have synthesized an SM-conjugated superoxide dismutase (SOD) derivative (SM-SOD) that circulates bound to albumin with a half-life of 6 h. Kinetic analysis revealed that SM-SOD effectively inhibited the superoxide-dependent reduction of SMAC either in the presence or absence of 0.5 mM albumin. However, the reduction of the circulating SMAC was not inhibited by SM-SOD both in normal and paraquat-treated animals. Plasma samples from both animal groups also reduced cytochrome c and SMAC by an SOD-insensitive mechanism. However, after treatment with ascorbate oxidase, both plasma samples lost their activity to reduce cytochrome c and SMAC. These and other results suggest that ascorbyl radical might principally be responsible for the reduction of circulating SMAC and that plasma levels of ascorbyl radical might increase in paraquat-treated animals.
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PMID:Synthesis of a cytochrome c derivative with prolonged in vivo half-life and determination of ascorbyl radicals in the circulation of the rat. 131 36

We evaluated a colorimetric method for the assay of uric acid in serum or urine, which utilises a Trinder chromogenic system modified by the inclusion of 2,4,6-tribromo-3-hydroxybenzoic acid for oxidative coupling to p-aminophenazone. Colour development (Amax: 512 nm) is complete within five minutes. Measurement of a sample blank is not needed. The procedure involves pre-incubation with ascorbic acid oxidase and detergent to eliminate interference by ascorbic acid and to abolish turbidity due to lipaemia; this pretreatment was effective up to 1.14 mmol/l ascorbate and up to at least 25 mmol/l triacylglycerol. Interference by icteric sera was insignificant up to about 170 mumol/l bilirubin. The method is linear up to at least 1428 mumol/l. In human serum and urine the procedure correlates well with HPLC and the uricase p-aminophenazone method on the SMAC analyser. Within-run and between-run imprecisions of the enzymic test were higher than for HPLC, but did not exceed 1.2% (CV) and 2.5% (CV), respectively.
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PMID:An enzymic assay for uric acid in serum and urine compared with HPLC. 270 44

Quantitation of the superoxide radical and its related metabolites in vivo is practically difficult predominantly because of their short biological half-lives. Though oxidized cytochrome c (cyt c) has been used for determining superoxide radicals in vitro, it cannot be used for in vivo analysis because of its low specificity as an electron acceptor and rapid disappearance from the circulation. To measure superoxide radicals and related metabolites in normal and pathologic subjects, we have synthesized a cyt c derivative (SMAC) with prolonged half-life in the circulation (T1/2 = 130 min) by conjugating acetylated cyt c with poly(styreneco-maleic acid) butyl ester (SM). An SM-conjugated superoxide dismutase (SM-SOD) with prolonged in vivo half-life was also synthesized. When injected intravenously to the rat, SMAC was rapidly reduced in the circulation of normal rats. The rate of SMAC reduction was markedly increased by intravenous administration of menadione, a compound capable of redox cycling and generating superoxide. The rate of SMAC reduction was not inhibited by a large dose of SM-SOD (27,000 unit/kg) in both normal and menadione-treated animals. The rate of SMAC reduction also increased in animals which were administered alloxan, a diabetogenic agents. In contrast to the experiments with menadione, the alloxan-enhanced reduction of SMAC was significantly inhibited by SM-SOD. Kinetic analysis using ascorbate oxidase suggested that ascorbyl radical was principally responsible for the SM-SOD-insensitive reduction of SMAC. Streptozotocin, another diabetogenic agent, failed to increase the rate of SMAC reduction. Thus, the effect of streptozotocin on the redox state of animals and the mechanism of its diabetogenic action might differ from those of alloxan. Combined use of SMAC and SM-SOD might permit quantitative studies on the occurrence of ascorbyl and superoxide radicals in the circulation of animals challenged with oxidative stress.
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PMID:Determination of superoxide and ascorbyl radicals in the circulation of animals under oxidative stress. 813 44