Yeast 3‐Phosphoglycerate Kinase

Abstract

The mechanism of the transphosphorylation reaction catalyzed by yeast 3‐phosphoglycerate kinase has been studied by means of spectrophotometric investigations. The binding sites, one for the nucleotide substrates and one for the acceptor, have been characterized. The interaction of nucleotide substrates with the enzyme, which is not metal‐dependent, resulted only in a perturbation of the spectrum of the nucleotide chromophore characterized by hypochromic and red shift effects. The hydrophobicity of this site was estimated by using a reporter group reagent, 2‐(dansylamino)ethyl monophosphate. The interaction of 3‐phosphoglycerate with its corresponding site produced perturbation of a tyrosyl chromophore. Furthermore, spectrophotometric studies evidenced the formation of binary and ternary complexes in accord with a random reaction mechanism proceeding via interconversion of ternary complexes. We also observed partial exchange reaction between ATP and ADP. Properties of this exchange reaction have been investigated. The partial reaction points out the existence of a covalent phosphoryl‐enzyme intermediate.