The cellular distribution of some rat-kidney glycosidases

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Abstract
Free and total activities of [beta]-glucosaminidase and [beta]-glucuronidase were determined fluorimetrically in five subcellular fractions of rat kidney. The [beta]-glucosidase activity appeared in the soluble fraction, [beta]-glucuroni-dase had the distribution pattern of a lysosomal enzyme, and both [beta]-galactosidase and N-acetyl-[beta]-glucosaminidase had bimodal distributions. Two types of [beta]-galactosidase activity were found: a sedimentable type, having optimum pH 3.7, molecular weight (mol-wt.] about 80,000 and slow electrophoretic mobility at pH 7.0 in starch gel; and a soluble type of much faster mobility, having optimum pH 5.5-6.5 and mol. wt. about 40,000. Evidence is presented that the [beta]-glucosidase and the soluble type of [beta]-galactosidase and the soluble type of [beta]-galactosidase are the same enzyme. Most of the N-acetyl-[beta]-glucosaminidase activity was in the lysosome-rich fractions, but a significant proportion occurred in the microsomal fraction in a non-latent form. The use of [beta]-galactosidase and N-acetyl-[beta]-glucosaminidase as lysosomal marker enzymes is complicated by the possible presence of multiple forms, but this limitation does not apply to 1-glucuronidase in the rat kidney.