COMPARISON OF THE ATPASE ACTIVITIES OF BOVINE HEART AND LIVER MITOCHONDRIAL ATP SYNTHASES WITH DIFFERENT TISSUE-SPECIFIC GAMMA-SUBUNIT ISOFORMS

The kinetics of heart and liver mitochondrial ATPase (FoF(1)) were exa mined using submitochondrial particles (SMPs) purified from the two ti ssues to obtain information on the role of gamma subunit isoforms. The F-1 portion is mainly composed of the catalytic, common alpha beta su bunits and tissue-specific gamma subunits. In contrast to the previous reports on the kinetics and crystallography of various F-1's, the Vma x and Km of the two isoforms of FoF(1) were identical although the SMP s were prepared from different tissues. Moreover sodium azide inhibite d the two equally. The ATPase activity of liver SMP showed slightly st eeper pH-dependency than that of heart SMP but the pH optima of the tw o were the same (pH 8). (C) 1994 Academic Press, Inc.