The incorporation of uridine 5′-triphosphate into ribonucleic acid by enzyme fractions from Ehrlich ascites carcinoma cells

Abstract

Fractionation of extracts of Ehrlich ascites carcinoma cells with ammonium sulphate yields two fractions which catalyse the incorporation of uridine 5′-triphosphate labelled with 32P or 14C into polyribonucleotide. With one of these, Fraction A, the incorporation of uridine triphosphate is greatly increased by the addition of a mixture of the 5′-triphosphates of adenosine, guanosine and cytidine and in these conditions most of the incorporated radioactivity is distributed in internucleotide linkages. Fraction B catalyses less extensive incorporation of uridine 5′-triphosphate, much of which is located terminally. This reaction is unaffected by the addition of a mixture of the 5′-triphosphates of adenosine, guanosine and cytidine, but is greatly stimulated by a mixture of amino acids. Both systems are inhibited by inorganic pyrophosphate.