Inhibition studies of carbamoyl phosphate synthetase from Escherichia coli

Carbamoyl phosphate synthetase (CPS) catalyzes the formation of carbamoyl phosphate (CP) from MgATP, bicarbonate, and glutamine. It has three active sites, one present on the small subunit and the two phosphorylation sites present on the large subunit. These two nucleotide binding sites are homologous. Six compounds were designed to mimic the reactive intermediate species carboxy phosphate, and product cabamoyl phosphate. The apparent Ki values calculated estimated the inhibitory strengths of these compounds. These plots were also utilized in identifying the linear inhibitors, nonlinear inhibitors and partial inhibitors. Inhibition patterns were obtained with these compounds using various assay formats. Partial inhibition displayed by phosphono formate for the full biosynthetic reaction can be utilized in support of the sequential mechanism for CPS.