title: Evidence for a tyrosine residue at the active site of phosphoglucomutase and its interaction with vanadate.
abstract: The rate of transfer of [32P]phosphate from [32P]-labeled phosphoglucomutase (alpha-D-glucose-1,6-bisphosphate:alpha-D-glucose-1-phosphate phosphotransferase, EC 2.7.5.1) to glucose increases dramatically between pH 8.5 and 10.5 with a half maximal rate at pH 9.8. This suggests the participation of a residue containing an ionizable group with a pK close to 10. The inhibition of enzyme activity obtained with tyrosine-derivatizing reactions--iodination, nitration, acetylation, and diazo coupling--is strongly indicative of tyrosine participation. Thiol reagents, p-hydroxymercuribenzoate and ethyleneimine, were without effect. Vanadate and arsenate augmented the transfer reaction 200- and 2.5-fold, respectively, and lowered the pH optimum of the reaction.
mesh_terms: D000818:Animals; D001391:Azo Compounds / Q000494:pharmacology; D001665:Binding Sites; D006863:Hydrogen-Ion Concentration; D007454:Iodides / Q000494:pharmacology; D007700:Kinetics; D009132:Muscles / Q000201:enzymology; D010733:Phosphoglucomutase / Q000378:metabolism*; D011817:Rabbits; D013774:Tetranitromethane / Q000494:pharmacology; D014443:Tyrosine; D014639:Vanadium / Q000494:pharmacology*
chemical_list: D001391:Azo Compounds; D007454:Iodides; D014639:Vanadium; D014443:Tyrosine; D010733:Phosphoglucomutase; D013774:Tetranitromethane