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Updated: Aug 8, 2026

Uracil-DNA Glycosylase Assay by Matrix-assisted Laser Desorption/Ionization Time-of-flight Mass Spectrometry Analysis
Published on: April 22, 2022
Uricase and allantoinase in glyoxysomes
1Division of Natural Sciences-I, University of California, Santa Cruz, California 95060.
Abstract:
In fat-degrading tissues of seedlings of seven different plant species examined, uricase activity (urate:O(2) oxidoreductase, EC 1.7.33) was associated with particulate fractions. After equilibrium density centrifugation on sucrose density gradients the enzyme activity was recovered in the glyoxysomal band (density: 1.25 grams per cubic centimeter). Allantoinase is also present in glyoxysomes but, equally, in the proplastid region (density: 1.22 grams per cubic centimeter). Xanthine oxidase, xanthine dehydrogenase, allantoicase, and urease were not detected in glyoxysomes from castor bean endosperm. Uricase in these particles shows its maximal activity at pH 8.9. The apparent K(m) is 7.4 mum. Urate concentrations greater than 120 mum as well as certain other purine compounds inhibit the enzyme. Cyanide at a concentration of 10 mum is a potent inhibitor. 2,6-Dichlorophenolindophenol did not substitute for oxygen as electron acceptor.
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