CHARACTERIZATION OF POLYPHOSPHATASE ACTIVITY IN ISOLATED-MITOCHONDRIAOF THE YEAST SACCHAROMYCES-CEREVISIAE

Saccharomyces cerevisiae mitochondria possess a polyphosphatase activi ty insensitive to a number of inhibitors of ATPase and pyrophosphatase (PPase) of the same organelle. Heparin (20 mu g/ml) and EDTA (0.5 mM) do not alter the ATPase and PPase activities and inhibit completely t he polyphosphatase activity. The mitochondrial polyphosphatase activit y is optimal at neutral pH. It is inhibited by monovalent cations in t he presence of Tris(+) in the order K+ > Na+ > NH4+ stimulated by diva lent cations in the order Co2+ > Mg2+ > Zn2+ > Mn2+. The polyphosphata se activity is nearly the same with polyphosphates ranging from 9 to 2 08 phosphate residues, but more than tenfold lower with tripolyphospha te. The polyphosphatase activity of mitochondria differs in some prope rties from that of the cell envelope, cytosol, vacuoles, and nuclei of the same S. cerevisiae strain.