II. Die Aktivität der GluDH und ihrer Untereinheiten : Influence on Molecular Weight and Activity of Bovine Liver Glutamate Dehydrogenase (GluDH) by Various Effectors in Vitro. II. The Activity of GluDH and its Subunits

The influence of Diethylstilboestrol (DES), Dihydro-DES, and some steroids on the enzymatic activity of glutamate dehydrogenase (GluDH) from beef liver was studied. In relation to the enzyme concentration in mg/ml the activity shows a maximum. This maximum fails when the turnover number is used as a measure for the enzyme activity. 10⁻⁵ M DES inhibits the GluDH activity almost completely, Dihydro-DES, Cyproterone and Cyproterone-acetate show no inhibition. The influence of Progesterone and Testosterone is about 20% and 10% respectively of that of DES. Dialysis will overcome the inhibition completely, to a smaller rate (about 30%) the addition of 10⁻³ M ADP too. It seems not to be necessary to suggest that there are two kinds of subunits of GluDH, the one corresponding to simple dilution, the other to treatment with DES.