Glucuronic acid phosphate

The possibility that a D-glucuronic acid phosphate is an intermediate in the conjugation mechanism has been visualized, but no evidence has yet been found as to its participation. Touster and Reynolds22 have added /3-D-glueuronic acid 1-phosphate and lactate to mouse liver slices, and have found that it neither stimulates nor inhibits synthesis of o-amino-phenyl D-glucosiduronic acid. The problem needs further study, with radioisotopes. 

About 20% of an oral dose of [ H] phylloquinone is excreted in the feces unchanged, suggesting that 80% is absorbed. A further 35% to 40% of the radioactivity is recovered in the feces as a variety of conjugates of polar metabolites formed by methyl oxidation of the side chain, followed by successive -oxidation, as well as reduction of the quinone ring to the quinol, to provide the site for conjugation with glucuronic acid, phosphate, or sulfate. About 75% of the conjugates are excreted in the bile and the remainder in the urine. In... 

Abbreviations NADPH, b-nicotinamide adenine dinucleotide phosphate reduced from 5 -phosphosulfate UDPGA, uridine diphosphate-glucuronic acid. 

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... 

---