Dissociation and Rate Constants of Some Human Liver Alcohol Dehydrogenase Isoenzymes.

Abstract

ADH [alcohol dehydrogenase] from human liver formed binary complexes with NADH, associated with a blue shift of the peak of the fluorescence emission of NADH. The wavelength shift was the same for all isoenzymes but the accompanying intensification of the fluorescence was different. The fluorescence is further increased by the formation of the very tight ternary enzyme-NADH-isobutyramide complexes. These properties are similar to those for the horse liver ADH, as well as the MW of E [ADH monomer] = 40,000/active site of the dimer molecule (EE). Stopped-flow determined velocity constants (ER .dblarw. E + R) were in good agreement with ethanol activity constants previously determined by activity measurement, confirming the validity of the ordered ternary complex mechanism also for the human ADH. No single isoenzyme activity as high as that reported by Mourad and Woronick or Drum was found.