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Biomedical subjects

W L Richards

Publications and source records attributed to W L Richards.

22 records · Page 2Linked to original sources
PubMed1978

Metabolite control of L-fucose utilization.

Thyroid fucokinase is responsive to a number of metabolites which might serve in a regulatory capacity. In addition to inhibition by ADP and stimulation by GMP, fucokinase responds selectively to a series of nucleotide sugars. Of those studied, only guanine nucleotide sugars moderate the activity of the enzyme. GDP-alpha-D-mannose, GDP-alpha-D-glucose, GDP-alpha-D-rhamnose, and GDP-alpha-L-fucose on the other hand is strongly inhibitory. In the case of GDP-alpha-D-mannose stimulation, a physiological role seems possible, but the rationale is not entirely clear. The effects of GDP-beta-L-fucose, on the other hand may represent physiological control effected through feedback inhibition by and end product.

Animals↗
PubMed1977

Canine thyroid fucokinase.

A radiometric assay was developed for fucokinase (ATP:6-deoxy-L-galactose 1-phosphotransferase, EC 2.7.1.52) based on the conversion of L-[14C]fucose to L-[14C]fucose 1-phosphate which is trapped and counted on ion exchange paper. This assay was used to detect the presence of a fucokinase in canine thyroid tissue which was subsequently purified 2754-fold over the crude tissue extracts. The product of the fucokinase was identified as the beta-anomer. The pH versus activity curve for the enzyme appears biphasic with optima at pH 6.5 and pH 8.25. The enzyme was shown to be highly specific for L-fucose with a Km of 2.6 - 10(-5) M at pH 8.25. It was shown to be absolutely specific for ATP as a phosphate donor with a Km of 6.3 - 10(-4) M at pH 8.25. The enzyme requires a divalent cation. Mg2+ is slightly more effective than Mn2+ in meeting this need. The molecular weight of the enzyme has been determined to be 494 000 +/- 12 400.

Animals↗