MODIFICATION OF THE PH-DEPENDENCE OF ANIMAL AND PLANT-TRANSPORT ATPASES BY SULFATED POLYSACCHARIDES

The effects of heparin and dextran sulfate 8,000 on two isoforms of th e sarco/endoplasmic reticulum Ca2+-ATPase of different animal tissues and on the corn root H+-ATPase were examined. In the absence of sulfat ed polysaccharides the pH profile's of the three transport ATPases wer e quite different, but after the addition of heparin or dextran sulfat e 8,000 the pH profiles of the three enzymes became similar, all showe d maximal activity at pH 7.0. Potassium and sodium antagonized the eff ects of sulfated polysaccharides on the three transport ATPases, but t he antagonism was considerably reduced at acidic pH values. (C) 1998 A cademic Press.