The activity of
uridine-cytidine kinase (Urd-Cyd
kinase). a key
enzyme in the salvage of
pyrimidine nucleosides, averaged 0.86 +/- 0.16 (S.E.M.) nmole
uridine phosphates . min-1 . (mg protein)-1 in fifty-three specimens of human colorectal
adenocarcinomas. The activity of
fluorouracil phosphoribosyltransferase (
FUPRTase) in thirty-five
carcinoma specimens averaged only 0.19 +/- 0.07 nmole fluorouridine
phosphates . min-1 . (mg protein)-1. The activity of the last
enzyme in the de novo pathway of biosynthesis of
UMP, i.e.
orotidine 5'-monophosphate (
OMP) decarboxylase, averaged 0.21 +/- 0.04 nmole CO2 . min-1 . (mg protein)-1. The activity of Urd-Cyd
kinase was increased approximately 2.3-fold, and that of
OMP decarboxylase by about 91%, while that of
FUPRTase was increased by only 27%, as compared to that of normal human colonic mucosa. Of the
colorectal carcinomas studied, 72% were moderately differentiated, 21% poorly differentiated, and 7% well differentiated. The mean diameter of the fifty-three
carcinomas was 5.5 cm, and pathologic staging led to classification of 15% as Dukes' A, 36% as Dukes' B, 47% as Dukes' C, and 2% as
carcinoma in situ. No correlations between the level of the
enzyme activities studied and any pathologic characteristics of the
carcinomas could be discerned.