Analysis of Allosteric mechanism in bacterial L-lactate dehydrogenases

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1. X-ray crystal analysis of mutant enzyme : Mutant enzymes in which arginine-173 or histidine-188 in FBP-binding site were replaced to glutamine or tyrosine were obtained. Preliminary analysis of the enzymes showed that the histidine residue is necessary for the binding of FBP.2. Analysis of substrate inhibition : Replace experiments showed that serine-193 and serine-318 play an important role for determining Michaelis and inhibition constants.3. X-ray analysis of crystal which comprises both T and R forms of the LDH : Crystal analysis revealed that there are enzyme molecules in both T and R states in a single crystal. Both molecular structure were analyzed in 2.5 angstrom resolution.4. Molecular mechanism of allosteric phenomena : Binding of FBP in T state overcomes electrostatic repulsion between subunits in P-axis. This induces rotation among four subunits and makes the active site active by interaction between subunit in Q-axis.