Glucuronic acid-1 - -phosphate, substrate

Preliminary studies by Arias et al. (A5) using 4-methylumbelliferone as a substrate indicate that glucuronides can also be synthesized from a-glucuronic acid-1-phosphate by an enzyme system present in the soluble fraction of rat liver homogenates. It is not yet known whether such a system is capable of conjugating bilirubin. 

In the presence of a-lactalbumin, however, only glucose and cellobiose (Glc)3l-4Glc) [37] are the preferred acceptors. Neither o-mannose, D-allose, D-galactose, o-ribose, nor D-xylose are substrates. Glucuronic acid and a-glucose-1-phosphate (monosaccharides with a negative charge) are also not accepted. 

To date, four main types of catalytic activity have been reported in detail for thermal polyamino acids. These are (with the most studied substrates in parentheses) hydrolyses (p-nitrophenyl acetate, p-nitro-phenyl phosphate, ATP), decarboxylations (OAA, glucuronic acid, pyruvic acid), and aminations (a-ketoglutaric acid, OAA, pyruvic acid, phenylpyruvic acid). The fourth type is a deamination reaction yielding a-ketoglutaric acid (51). For some of the actions of the thermal polymers the products are identified quantitatively, and the kinds of amino acid side chain necessary for activity in the polymer elucidated. In others, products have yet to be fully identified. The activities of thermal polyamino acids are manifest on substrates which range from chemically labile to relatively stable. 

SI Houet, R., Duchateau, G., and Florkin, M., Compt. rend. soc. bid. 1S6, 412 (1941). ss However, note the recent report of Dutton and Story on the isolation of uridine diphosphate glucuronic acid. Furthermore, new methods for the synthesis of the a- and /3-glucuronic acid-l-phosphates. (Marsh, C. A., J. Chem. Soc. 1963, 1578) have made these compounds readily available for enzymatic study. In this connection it is of interest that the /J-glucuronic acid-l-phosphate is hydrolyzed by /3-glucuronidase, although this substrate was not found to be effective in glucuronide formation. (Levvy, G. A., and Marsh, C. A., Bioekem. J. 62, 690 (1952).)... 

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