DEIMINATION OF GLYCOGEN-PHOSPHORYLASE-B BY PEPTIDYLARGININE DEIMINASE- INFLUENCE ON THE KINETIC CHARACTERISTICS AND DIMER-TETRAMER TRANSITION

The kinetics of the native glycogen phosphorylase b from rabbit skelet al muscle and of the enzyme specifically deiminated by peptidylarginin e deiminase have been studied. One arginine residue per phosphorylase b monomer is transformed into citrulline after 3 h of incubation with peptidylarginine deiminase. The maximal velocity of the enzymatic reac tion for the modified phosphorylase b is 7-20% higher than that for th e native enzyme. Deiminated phosphorylase b, like the native enzyme, s hows a positive kinetic cooperativity with respect to glucose-1-phosph ate. The affinity of the modified phosphorylase b for the allosteric a ctivator AMP is one order of magnitude higher than that of the native enzyme. Deimination caused a pronounced reduction of the values of [I] (0.5) for FMN and glucose, but the sensitivity of the deiminated enzym e to glucose-6-phosphate is much lower than that of the native phospho rylase b. Deiminated phosphorylase b, unlike the native enzyme, shows the positive cooperativity for FMN binding. Deiminated phosphorylase b , unlike the native enzyme, shows less capability to form tetramers in the presence of AMP as compared to the native enzyme.