MODULATION OF THE ALLOSTERIC EQUILIBRIUM OF YEAST CHORISMATE MUTASE BY VARIATION OF A SINGLE AMINO-ACID RESIDUE

Chorismate mutase (EC 5.4.99.5) from the yeast Saccharomyces cerevisia e is an allosteric enzyme which can be locked in its active R (relaxed ) state by a single threonine-to-isoleucine exchange at position 226. Seven new replacements of residue 226 reveal that this position is abl e to direct the enzyme's allosteric equilibrium, without interfering w ith the catalytic constant or the affinity for the activator.