Muscle pyruvate kinase: interaction with substrates and analogues studied by difference spectroscopy. Comparative studies of the substrate-binding sites of various ATP phosphotransferases.

The substrate binding sites of pyruvate kinase have been studied by means of spectrophotometric investigations. Two binding sites, one for the nucleotide substrate and one for the acceptor, have been characterized. The interaction of nucleotide substrates with the enzyme, which is metal-dependent, results in a perturbation of the spectrum of the nucleotide chromophore characterized by hypochromic and red shift effects; the hydrophobicity of the nucleotide site was estimated by using a reporter group reagent, 2-(dansylamino)ethyl monophosphate. The comparison between the binding sites of several ATP phosphotransferases is discussed and some common features are reported.