Regulation of Allantoin and Allantoic Acid Degradation in the Yam and Sweet Potato

Document Type

Article

Publication Title

Journal of Agricultural and Food Chemistry

Abstract

In the regulation of allantoin and allantoic acid degradation in root tubers, allantoic acid is the substrate for allantoicase and allantoate amidohydrolase while allantoin is the substrate for allantoinase. The allantoate amidohydrolase is not influenced by urea and glyoxylate, whereas allantoicase is activated by both compounds in yam tubers but inhibited by glyoxylate in the sweet potato. Thus, allantoate amidohydrolase with a lower apparent Kmthan allantoicase controls the anabolic degradation, whereas allantoicase controls the catabolic degradation of allantoic acid. Glyoxylate and urea inhibit the degradation of allantoin by allantoinase, which responds allosterically to varying concentrations of allantoin, urea, and glyoxylate. High concentrations of urea (ca. 0.4 mM) and glyoxylate (ca. 4 mM) induce the tuber allantoinase to catalyze the synthesis of allantoin using glyoxylate and urea as substrates. Allantoinase appears to be the enzyme that regulates the overall rate of purine catabolism and synthesis in root tubers. © 1987, American Chemical Society. All rights reserved.

First Page

219

Last Page

223

DOI

10.1021/jf00074a013

Publication Date

3-1-1987

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