Abstract
Isotope effect studies have shown that malic enzyme from avian liver or Ascaris suum has a stepwise mechanism with NAD(P) as substrate, but a concerted one with nucleotide substrates with higher redox potentials. It has been possible to calculate intrinsic deuterium and 13C isotope effects and commitments. The enzyme is very specific, with only erythro-fluoromalate, D- and mesotartrate and L-aspartate with an unprotonated amino group as slow alternate substrates.