Probing the catalytic allosteric mechanism of rabbit muscle pyruvate kinase by tryptophan fluorescence quenching.

Pyruvate kinase acts as an allosteric enzyme, playing a crucial role in the catalysis of the final step of the glycolytic pathway. In this study, site-specific mutagenesis and tryptophan fluorescence quenching were used to probe the catalytic allosteric mechanism of rabbit muscle pyruvate kinase. Movement of the B domain was found to be essential for the catalytic reaction. Rotation of the B domain in the opening of the cleft between domains B and A induced by the binding of activating cations allows substrates to bind, whereas substrate binding shifts the rotation of the B domain in the closure of the cleft. Trp-157 accounts for the differences in tryptophan fluorescence signal with and without activating cations and substrates. Trp-481 and Trp-514 are brought into an aqueous environment after phenylalanine binding.