Abstract
Acid extracts from tissues of two solanaceous plants were found to contain a heat-labile, nondialyzable factor which hydrolyzes nucleoside di- and triphosphates to nucleoside monophosphates. This acid-resistant factor shows optimal ATP-hydrolyzing activity at pH 5, whereas practically no activity was detected below pH 3 and above pH 9. It does not hydrolyze sugar phosphates, nucleoside monophosphates, uridine diphosphoglucose, and phosphoenolpyruvate. In order to estimate quantitatively the amount of nucleoside di- and triphosphates in a plant extract, care must be taken to circumvent possible interference by this factor. This is achieved by carefully maintaining the extract below pH 3.