Carnitine palmityltransferase activity during myocardial ischemmia and at low ionic strengths

Carnitine palmityltransferase activity was measured in mitochondria isolated from control and ischemic dog heart. The ischemic activity demonstrated a decrease in both the Vmax and the Km of the enzyme for 1-carnitine when measured in the presence of 160 muM palmityl-CoA. The kinetic response of the mitochondrial carnitine palmityltransferase to ischemia was mimicked by assay of the enzyme from control mitochondria in a medium of low ionic strength. The effect of ionic strength on enzyme activity was directly correlated with binding of palmityl-CoA to the mitochondrial membranes. The decrease in carnitine palmityltransferase activity in ischemic mitochondria may reflect a decrease in palmityl-CoA binding to the enzyme active site. The depression in ischemic carnitine palmityltransferase activity may represent an early defect in mitochondrial metabolism.