| Abstract: | Adenosine triphosphatase activity, present in extracts of isolatedphloem and xylem tissues of Heracleum mantegazzianum and thepetioles of Helianthus annuus, has been fractionated on 7 percent polyacrylamide gels into electrophoretically distinct enzymeswith different properties. Extracts of whole petioles containfour enzymes capable of hydrolysing ATP, phloem extracts possesstwo, and xylem, one. Enzyme I, common to all the extracts, showspreferential hydrolysis of nucleoside triphosphates and is stimulatedby 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 unaffectedby monovalent cations. All four enzymes are markedly inhibitedby Mg2+. None of the enzymes is affected by ouabain or oligomycin. |
