Crystalline Lactic Dehydrogenase of the Lens.

A protein with low LDH activity compared to recrystallized muscle LDH and one which appeared to be homogeneous by all available tests for protein homogeneity has been obtained in crystalline form from bovine and rabbit lenses. These lens LDH preparations appeared to be identical immunologically in the other mammalian species examined. The bovine lens LDH had half the molecular weight of LDH isozymes isolated from bovine heart. The LDH activity of bovine lenses in certain chemical tests was found to be both similar and different when compared to bovine heart LDH. This also teas the situation with rabbit lens LDH compared with a commercial preparation of rabbit muscle LDH. During a study of the reaction of bovine lens LDH with metallic salts, ZnSO* and HgCh in particular, it was noted that the LDH activity became soluble in 2.6M ammonium sulfate, became less stable, and disappeared as a distinct band on disc electropherograms in acrylamide gel. The chemistry of this transformation in the solubility of LDH suggests that a metal chelate bond was broken by the treatment concomitant with the appearance of a quite unstable low molecular weight fragment toith increased LDH activity. Confirmation of this impression awaits success of efforts to isolate such a fragment.