Effects of nonenzymatic glycation of subfragment-1 of myosin on interactions with actin.

Nonenzymatic bonding of reducing sugars to subfragment-1 of myosin (S-1) resulted in a reduction in actin-activated S-1 ATPase activity. Fructose caused a greater reduction than glucose. The Km for binding of actin to S-1 was significantly increased with sugar derivatization. In addition, sugar derivatization lowered the ability of S-1 to promote polymerization of G-actin. Western blot analysis demonstrated that glucose was nonenzymatically incorporated into the 50 and 20 kilodalton (kDa) fragments of S-1 with preponderance in the 20-kDa fragment. The reduced affinity of derivatized myosin for actin is indicated by the increased Km, the reduced ability to stimulate actin polymerization, and the positive Western blot reaction in the 20-kDa fragment.