Glucuronic acid-l-phosphate

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).)... 

All the enzymes of the hexose monophosphate shunt have been found in the supernatant fraction of the cell. The enzymes of the glucuronic pathway, with the exception of NADP-L-hexonate dehydrogenase and aldonolactonase, which are found in the supernatant fraction of the cell, have a complex intracellular distribution. All the enzymes involved in glucuronic acid-1-phosphate synthesis and in the conversion of glucuronic phosphate or glucuronic acid to L-xylose or ascorbic acid are associated with the endoplasmic reticulum. The enzymes involved in the conversion of L-xylose to D-xylose are found in mitochondria. Thus, the complete glucuronic pathway involves three different cell fractions. 

Isomers of D-apiofuranosyl 1-phosphate have been prepared by treating a mixture of jS-o-apio-D-furanosyl and /3-D-apio-L-furanosyl tetra-acetates with crystalline phosphoric acid. a-o-Apio-o- (59) and a-o-apio-L-furanosyl-1-phosphate (60) and their cyclic phosphates were separated by chromatography and identified by H n.m.r. o-Apiose is metabolized in parsley and Lemna minor with the possible formation of UDP-D-apiose. L. minor will convert UDP-a-glucuronic acid into a-o-apio-D-furanosyl-1,2-cyclic phosphate (61) but no evidence of UDP-o-apiose was found, although it is possible that (61) arose from the rapid hydrolysis of UDP-o-apiose. 

Incubation of a cell-free extract of L. minor in the presence of NAD+ and UDP-D-[U-14C]glucuronic acid generated two compounds, each containing a different radioactive C5 sugar.96 The presence of apiose after hydrolysis was diagnosed by (a) paper chromatography, (b) specific complex-formation with benzeneboronic acid, (c) electrophoretic mobility, and (d) formation of its isopropylidene acetal. Treatment with ammonia at 0° showed that the compound was formed by a nonenzymic cyclization.96 Treatment with phosphoric diesterase plus phosphatase further supported an earlier report of the existence of a D-apiosyl cyclic phosphate.95... 

Figure 1. Inositol synthesis and catabolism. Inositol is synthesized from glucose-6-phosphate (Glucose 6-P) by the action of L-wyo-inositol 1-phosphate synthase (MIPS) and wyo-inositol monophosphatase (IMP). IMPase is also required for the last step of inositol (1,4,5)P3 second messenger breakdown. The first step in inositol catabolism utilizes the wyo-inositol oxygenase (MIOX) enzyme, which cleaves the inositol ring to form D-glucuronic acid.

Glucuronic acid pathway. The first part consists of synthesis of UDP-glucuronic acid and release of free D-glucuronic acid. The second part is the metabolism of D-glucuronic acid. D-Glucuronic acid is written as both the cyclic hemiacetal and the open-chain aldohexose and two orientations of L-gulonic acid and D-xylulose are shown. P = phosphate. 

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