PURINE AND PYRIMIDINE NUCLEOTIDE INHIBITION OF CARBAMYL PHOSPHATE SYNTHETASE FROM PEA SEEDLINGS

Carbamyl phosphate synthetase from Alaska pea seedlings is subject to inhibition by several pyrimidine and purine nuclotides. It is similar in some respects to the E. coli enzyme. Both have similar Ki values for UMP, the most potent inhibitor, and both show partial reversal of UMP inhibition by L-ornithine. However, the pea enzyme is inhibited by AMP and ADP, while the E. coli enzyme is stimulated by these compounds. The role of nucleotides and ornithine in strongly influencing the activity of carbamyl phosphate synthetase has obvious potential regulatory significance in the operation of the ornithine cycle and in pyrimidine nucleotide synthesis. © 1968.