ADP-GLUCOSE PYROPHOSPHORYLASE - EVIDENCE FOR A LYSINE RESIDUE AT ACTIVATOR SITE OF ESCHERICHIA-COLI-B ENZYME

Pyridoxal-P (phosphate) can be covalently linked to E. coli B ADP glucose pyrophosphorylase by reduction with sodium borohydride. The modified enzyme is almost fully active when less than 1 mol of pyridoxal-P is incorporated per mol of enzyme subunit and is no longer dependent on the presence of allosteric activators in reaction mixtures for high activity. The allosteric activators, fructose-P2 or hexanediol 1,6 bisphosphate, decrease the incorporation of pyridoxal-P into enzyme suggesting that the pyridoxal-P is linked at or near the allosteric activator binding site. Acid hydrolysis of the modified enzyme yields pyridoxyllysine, suggesting that the .epsilon. amino group of lysine is functional in the binding of the allosteric activators of the enzyme.