Sedimentation Coefficient and Molecular Weight of Beef Liver Glutamate Dehydrogenase at the Microgram and the Milligram Level

The molecular weight and the sedimentation behaviour of beef liver glutamate dehydrogenase was investigated in the range of protein concentration between 25 μg/ml and 8 mg/ml. sO20,ω was found to be 13.0 S. Light scattering experiments (at 20° and 4360 Å) and sedimentation equilibrium experiments performed in M/15 potassium sodium phosphate buffer, pH 7.6, show that the molecular weight of the smallest enzymatically active subunit is 280,000 and that the associated enzyme molecule (molecular weight about 2.2 millions) is formed by association of eight subunits. From the dependence of the apparent molecular weight of the protein concentration and from the comparison with calculated curves it follows that the associated enzyme molecule is formed in a stepwise association‐dissociation equilibrium and not in a closed equilibrium between monomers and the octamer without any intermediate steps.