Fractionation of monovalent ion-stimulated nucleoside triphosphatase activity in extracts of petiolar tissues

Adenosine triphosphatase activity, present in extracts of isolated phloem and xylem tissues of Heracleum mantegazzianum and the petioles of Helianthus annuus, has been fractionated on 7 per cent polyacrylamide gels into electrophoretically distinct enzymes with different properties. Extracts of whole petioles contain four enzymes capable of hydrolysing ATP, phloem extracts possess two, and xylem, one. Enzyme I, common to all the extracts, shows preferential hydrolysis of nucleoside triphosphates and is stimulated by monovalent cations. Enzyme II, of phloem and of petiole extracts, is a general phosphatase. Enzymes III and IV, of petiole extracts, are specific for nucleoside triphosphates but are unaffected by monovalent cations. All four enzymes are markedly inhibited by Mg2+. None of the enzymes is affected by ouabain or oligomycin.