KINETICS OF WATER-INSOLUBLE PHOSPHOGLYCERATE MUTASE

1. 1.|An insoluble form of phosphoglycerate mutase (2,3-diphospho-d-glycerate: 2-phospho-d-glycerate phosphotransferase, EC 2.7.5.3) from rabbit muscle was prepared by mechanically immobilizing the crystalline enzyme within a water-insoluble carrier of highly cross-linked polyacrylamide. This procedure has previously been devised in our laboratory and is known to involve no covalent bonds between enzyme and carrier. 2. 2.|The kinetic behavior of the soluble and insoluble forms of this enzyme were identical in many respects, i.e. upon variation of the enzyme concentration, substrate concentration and temperature. Thus, their Michaelis constants, activation energies and susceptibilities to substrate inhibition were the same. 3. 3.|In contrast, the pH optimum of activity of the insoluble form of mutase was one whole unit lower than that of the water-soluble form, although the carrier of the insoluble enzyme was electrostatically neutral. 4. 4.|Insoluble mutase was also more sensitive to activation by 2,3-diphosphoglycerate than the soluble form. 5. 5.|A comparison between the insoluble forms of phosphoglycerate mutase and enolase, prepared by the same procedure, shows that differences between soluble and insoluble forms of these enzymes depend more on the nature of the enzyme than on that of the insoluble carrier. © 1969.