Action of 5-thio- d-glucose and its 1-phosphate with hexokinase and phosphoglucomutase

Previous work from this laboratory has shown that 5-thio- d-glucose is a competitive inhibitor for active transport of d-glucose. The present work indicates that the thiosugar analog and its 1-phosphate can also interfere with d-glucose 6-P formation. 5-Thio- d-glucose serves as a substrate for yeast hexokinase with a K m of 4 m m, and V of 8.8 nmol/min/μg of protein. The analog competitively inhibits d-glucose phosphorylation with a K i of 20 m m. 5-Thio- d-glucose 1-P can act as a substrate for rabbit skeletal muscle phosphoglucomutase with a K m of 60 μ m and V of 0.17 μmol/min/μg of protein. Thus, 5-thio- d-glucose 1-P behaves as a near metabolic analog of d-glucose 1-P. 5-Thio- d-glucose 1-P is a competitive inhibitor of d-glucose 1-P conversion to the 6-P with a K i of 16.2 μ m. 5-Thio- d-glucose 6-P produced by phosphorylation of 5-thio- d-glucose and by conversion from 5-thio- d-glucose 1-P was identified by chromatographic mobility and by color reactions.