Muscle D-glyceraldehyde-3-phosphate dehydrogenase from Caiman sp. II New data for enzyme characterization

Muscle GPDH from Caiman sp. was activated by dithioerythritol and 2-mercaptoethanol. Maximal activation was obtained with the reducing agent at 10mM final concentration. The binding of NAD to the apoenzyme occurs at four sites per tetramer, but ligand affinity seems to be heterogeneous. Incubation of the holo or the apoenzyme with NADH at 37 degrees C caused inactivation of the enzyme, with partial loss of SH-titrable groups. Incubation of the holo or the apoenzyme with G3P at 37 degrees C caused partial inactivation of the enzyme. The apoenzyme was demonstrated to be more stable than the respective holoenzyme, in the assay conditions used.