SECONDARY ISOTOPE EFFECTS IN REACTIONS CATALYZED BY YEAST AND MUSCLE ALDOLASE

The aldolase-catalyzed condensation of (1.R)-[1-3H]dihydroxyacetone-P with D-glyceraldehyde-3-P to give [3- 3 H]fructose-l,6-diP was found to go more slowly than normal under conditions which previously indicated that the proton abstraction step is rate determining. Furthermore, slower reaction of fructose-diP containing 3 H at C-3 or C-4 is characteristic of both the yeast and muscle enzymes, indicating that the C-C cleavage step (kinetic effect) or glyceraldehyde-P release (equilibrium effect) is the rate-limiting step for the formation of the first product, glyceraldehyde-3-P. © 1969, American Chemical Society. All rights reserved.