Further characterization of collagen galactosyltransferase from chick embryos

Optimum extraction of collagen galactosyltransferase activity from chick embryos required relatively high concentrations of detergent and salt. The activity was inhibited by concanavalin A, and the enzyme had a high affinity for columns of this lectin coupled to agarose; these results suggest the presence of carbohydrate units in the enzyme molecule. Collagen galactosyltransferase was highly labile, and only 1% of the originally bound enzyme activity could be eluted from the concanavalin A-agarose column with a buffer containing methyl glucoside and ethylene glycol. The purification of the activity over the original supernatant of chick embryo homogenate was 250-300-fold, with the optimum reaction conditions for the purified transferase differing somewhat from those for crude enzyme preparations. The reaction was inhibited by glucose-free basement-membrane collagen, UDP and galactosylhydroxylsine, and also by Co2+ and a number of compounds resembling UDP-galactose. Hydroxylysine was also a weak inhibitor. Immobilized hydroxylysine and UDP-glucuronic acid did not bind the collagen galactosyltransferase, but the enzyme was retarded in a column of UDP-galacturonic acid linked to agarose.