A colorimetric determination of inositol monophosphates as an assay for D-glucose 6-phosphate-1L-myoinositol 1-phosphate cyclase.
A rapid and convenient chemical assay for the enzyme d-glucose 6-phosphate-1l-myoinositol 1-phosphate cyclase is described. The 1l-myoinositol 1-phosphate formed enzymically was oxidized with periodic acid liberating inorganic phosphate, which was assayed. myoInositol 2-phosphate can be assayed in the same way. Glucose 6-phosphate and other primary phosphate esters gave only very small quantities of inorganic phosphate under the conditions described. The K(m) of the enzyme for d-glucose 6-phosphate, 7.5+/-2.5x10(-4)m, was identical with that measured by the radiochemical method. 2-Deoxy-d-glucose 6-phosphate was a powerful competitive inhibitor, K(i) 2.0+/-0.5x10(-5)m, but was not a substrate for the enzyme.
D000818:Animals; D003124:Colorimetry; D006600:Hexosephosphates; D007294:Inositol / Q000032:analysis*; D007700:Kinetics; D008297:Male; D008722:Methods; D010088:Oxidoreductases / Q000032:analysis*; D010504:Periodic Acid; D010756:Phosphoric Acids / Q000032:analysis*; D010744:Phosphoric Monoester Hydrolases; D051381:Rats; D013737:Testis / Q000201:enzymology
D006600:Hexosephosphates; D010756:Phosphoric Acids; D010504:Periodic Acid; D007294:Inositol; D010088:Oxidoreductases; D010744:Phosphoric Monoester Hydrolases