Abstract
Two enzymes, β-galactosidase and N-acetyl-β-glucosaminidase, have been detected in pigment epithelial cells of cattle. The optimum activity for N-acetyl-β-glucosaminidase is at pH 5; in contrast, β-galactosidase exhibits a broad activity maximum from approximately pH 4 to 6, with a "shoulder" in the latter range. Differential centrifugation of .25M sucrose-ethylenediamine tetraacetic acid (EDTA) homogenates showed that the highest specific activities were in the mitochondrial + lysosomal (M+L) fraction and in the fraction sedimenting at 6,000 g-minutes, i.e., the pigment granules + nuclei (PG+N). Agents, such as sonication, freezing-and-thawing, or homogenization with Triton X-100, known to induce osmotic shock or membrane rupture, resulted in the release of nearly all the enzymes from the particulates in the PG+N fraction.