Chromatin-associated nucleoside triphosphate diphosphatase (NTDPase) activity was detected in Alaska pea plant only at the germination stage in a study of the plant's development over 5 month from the dormant to fruiting stages. This enzyme activity was also detected in seedlings of several dicotyledonous plants including soybean, Usui pea, cowpea and cucumber, but almost none was found in monocotyledonous corn and rice plants.When the chromatin of pea epicotyl was fractionated into template-active and -inactive forms by DNase II digestion, most of the NTDPase activity was found in the active chromatin.A new method to rapidly isolate and purify NTDPase from pea epicotyl chromatin was developed in which NTDPase was eluted with a linear gradient of NaCl on a column packed with cellulose powder and chromatin. DNA remained on the column and the eluted NTDPase was purified further by chromatography using trimethylamino-2-hydroxypropyl cellulose (TMAP-cellulose) and a Sephadex G-100 column, which give chromatin 18-fold purer than the starting sample.This purified NTDPase was adsorbed by DNA-cellulose, which is further evidence that NTDPase is a kind of non-histone protein associated with DNA. Several cations including Ca2$, Mg2$, Mn2$and Zn2$stimulated the enzyme activity, with the maximal eightfold activation by Ca2$. NTDPase activity was clearly inhibited by KCN and pyrophosphate, but not by SH-blocking inhibitors and various metal chelators at 1 mM.
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