During purification and heat denaturation experiments the activity of orotidylic acid decarboxylase appears to parallel orotate phosphoribosyltransferase activity. Also under a variety of physiological conditions both enzymes show closely parallel, co-ordinate changes in activity [120–122]. Orotate phosphoribosyltransferase from murine leukaemia P 1534 J (utilizing as the substrate orotate and 5-fluorouracil) was found to exist as a complex with orotidylic acid decarboxylase (123). Both enzyme activities were eluted together during gel filtration, co-sedimented in sucrose gradients, and remainded associated during salt fractionation. However, they could be separated into a phosphoribosyltransferase and decarboxylase component when enzyme preparations previously subjected to limited proteolysis by elastase were sedimented in sucrose gradients F.
KeywordsSucrose Gradient Limited Proteolysis Ehrlich Ascites Carcinoma OROTIC Acid Carbamoyl Phosphate Synthetase
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