Effect of sulfhydryl group modification on age-associated alteration of actomyosin ATPase activity in human myocardium

Abstract

Cardiac ventricular actomyosin was prepared from autopsy samples from humans ranging in age from one to 83 years, and its Ca2(+)-ATPase and K(+)-EDTA-ATPase activities were determined in the presence or absence of a sulfhydryl reagent, N-ethylmaleimide (NEM). The Ca2(+)-ATPase activity increased in the presence of appropriate concentrations of NEM. The extent of the stimulation of Ca2(+)-ATPase activity by NEM decreased significantly with age. The ratio of K(+)-EDTA-ATPase activity to Ca2(+)-ATPase activity also decreased with age. This suggests that there is an age-related modification of sulfhydryl groups in the myosin molecule.