CHM362H5 Lecture Notes - Lecture 26: Carbamoyl Phosphate, Pyrimidine Metabolism, Phosphoribosyl Pyrophosphate
Document Summary
Pyrimidine synthesis pathway: starts with carbamoyl phosphate synthesis, committed step in pyrimidine biosynthesis in mammals, cps-ii is activated by prpp, atp (abundant energy and purines, cps-ii is inhibited by udp and utp, substrates are: hco3. Carbamoyl phosphate synthesis: step 1: formation of carboxy phosphate, step 2: displacement of phosphate group by side chain nh2 of gln carbamate, step 3: phosphorylation of carbamate carbamoyl phosphate. Pyrimidine synthesis building the ring: condensation of carbamoyl phosphate with asp carbamoyl-asp, catalyzed by aspartate transcarbamoylase (atcase, carbamoyl phosphate is activated" carbamoyl group no atp required. Synthesis of utp and ctp: udp is made from ump nucleoside monophosphate kinase. Udp + adp: utp is made from udp nucleoside diphosphate kinase. Utp + adp: ctp sythetase then forms ctp from utp and atp. Regulation of pyrimidine biosynthesis: at the cps-ii step, of the allosteric modulators, only atp is a substrate of cps-ii.
