Glucuronate reductase

Reddy, C.C., Swan, J.S., and Hamilton, G.A., 1981, myo-Inositol oxygenase from hog kidney. I. Purification and characterization of the oxygenase and of an enzyme complex containing the oxygenase and D-glucuronate reductase. J. Biol. Chem. 256 8510-8518. 

Figure 13.2. Biosynthesis of ascorbate. Glucuronate reductase, EC 1.1.1.19 glucono-lactone3-lactonase, EC 3.1.1.17 gulonolactone oxidase, EC 1.1.3.8 NADPH-dependent dehydroascorbate reductase, EC 1.6.5.4 and glutathione-dependent dehydroascorbate...

This reaction is considered to be catalyzed by NADPH-dependent D-glucuronate reductase, the enzyme that acts on D-glucuronic acid in the other pathway. For the formation of L-gulono-"y-lactone, Chatterjee et al. (1961) proposed the presence of a different enzyme attacking D-glucurono-7-lactone with the requirement of cyanide, but their proposal was later challenged (Sato et al., 1976). 

A.- ng deduction. This is an irreversible reaction which is a foremost determinant of the secretion rate of cortisol (double bonds and C-3 carbonyl). Catalyzed predominantiy by cortisone P-reductase and 3a-hydroxysteroid dehydrogenases, SP sterols result, although 5a sterols are more prevalent in the case of other glucocorticoids. Urocortisol and urocortisone result from the metabohsm of cortisol and cortisone, respectively. Compounds can be complexed to glucuronic acid at this point. 

Scheme 3.3 Chemoenzymatic conversion of D-glucuronic acid to L-ascorbic acid [59] NADPH-dependent uronate reductase A from Saccharomyces cerevisiae, cloned into . coli converted D-glucuronic acid at 90% yield. Chemical lactonization gave inter-...

Figure 22-1. Production of bilirubin (BR). The degradation of I e l 3-hcme by molecular oxygen and NAD PH, catalyzed by microsomal heme oxygenase, produces biUverdin, CO, and Fe+2. Subsequent reduction of biliverdin by NADPH, catalyzed by biliverdin reductase, produces bilirubin. Bilirubin that is produced in phagocytes from degradation of senescent erythrocytes is transported to liver for conjugation with glucuronic acid, catalyzed by bilirubin-UDP-glucuronyltransferase. In some cells, the bilirubin is used as an antioxidant, where it recycles through the biliverdin reductase reaction.

This is a harmless inborn error caused by a deficiency of l-xylulose reductase, an enzyme involved in the glucuronic acid pathway. 

NADP-specific xylitol oxidoreductase (t-xylose reductase) (EC 1.1.1.10). L-Xylulose is continuously excreted in large amounts in the urine. Administration of glucuronic acid further increases xylulose excretion. Benign. No treatment needed. See Glucuronate pathway. 

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