1. Halobacterium cutirubrum L-alanine dehydrogenase was purified approx. 100-fold. 2. It has a mol. wt. of 72 500, about one-third that of two well-studied alanine dehydrogenases from non-halophiles. 3. The activity of the enzyme increases with temperature up to 70 degrees C, but the protein itself is not thermostable. 4. In the reductive amination reaction, the enzyme is fully active in the presence of high concentrations of K+, Na+ or NH4+ and partially active with Cs+ or Li+, but for oxidative deamination it has an absolute requirement for K+.
