Preliminary studies of the uridine kinase activity of human colorectal adenocarcinomas

Relatively low uridine-cytidine kinase activities in 22 surgical specimens of human colorectal adenocarcinomas have been demonstrated, in comparison with those of other neoplasms studied. The kinase activities averaged 1.1 nmoles/min/mg of protein; however, four of the specimens exhibited significantly higher levels of enzyme activity than the average, a deviation that could not be correlated with any properties of the tumors. Of the 22 neoplasms, 86% were moderately differentiated; and 14% were poorly differentiated. Staging disclosed 9% Dukes' A neoplasms, 41% Dukes' B, and 50% Dukes' C. The moderately differentiated group included four mucinous tumors; the poorly differentiated only one; none was of the signet-ring cell type. The kinetic characteristics of the uridine kinase activity of one colonic adenocarcinoma were studied in detail; the apparent Michaelis constants for uridine and adenosine 5'-triphosphate were 0.37 x 10(-3) M and 1.07 x 10(-3) M, respectively, and the enzyme required Mg2+ for maximal activity (at 30-42 C).