SIGNIFICANCE OF THE ENZYMATIC-PROPERTIES OF YEAST S39A ENOLASE TO THECATALYTIC MECHANISM

The S39A mutant of yeast enolase (isozyme 1), prepared by site-directe d mutagenesis, has a relative V-max of 0.01% and an activation constan t for Mg2+ ca. 10-fold higher, compared with native enzyme. It is corr ectly folded. There is little effect of solvent viscosity on activity. We think that the loop Ser36-His43 fails to move to the 'closed' posi tion upon catalytic Mg2+ binding, weakening several electrostatic inte ractions involved in the mechanism. (C) 1998 Elsevier Science B.V.