Cytidine triphosphate polymerase activity associated with isolated chromatin of sugar beets

A nucleotidyltransferase associated with the chromatinrich fraction of sugar beet tissue has been isolated. The product of the enzyme-catalyzed reaction is a ribohomopolymer. The reaction requires Mg 2+ or Mn 2+ for activity. In the presence of Mg 2+ only CTP is utilized as substrate, however, in the presence of Mn 2+ , ATP, GTP, and UTP are also utilized but much less than CTP. When Mg 2+ is present at optimal concentration (37.5 m m ) the addition of Mn 2+ to the reaction inhibits CMP incorporation. Incorporation of CMP is inhibited by DNase I, trypsin, other nucleoside triphosphates (ATP, GTP, and UTP), and inorganic pyrophosphate, but not by pancreatic RNase and actinomycin D. It is concluded that the enzyme activity can be classified as a CTP-polymerase.