GLYCOSIDASES OF RETINAL-PIGMENT EPITHELIUM

  • 1 January 1978
    • journal article
    • research article
    • Vol. 17  (9) , 884-895
Abstract
The pH optima and apparent Km and Vmax values were determined for 9 glycosidases of the calf retinal pigment epithelium (RPE). In terms of .mu.mol of stubstrate cleaved per mg protein per h, the following relative order of enzymatic activities was observed: .beta.-N-acetylglusosaminidase > .alpha.-glucosidase = .beta.-N-acetylgalactosaminidase > .alpha.-mannosidase > .beta.-galactosidase > .beta.-glucosidase > .alpha.-fucosidase > .alpha.-galactosidase > .beta.-glucuronidase. The pH optimum of each of the enzymes was in the acidic range (below pH 6). These activities may relate to those activities associated with particulate components of the RPE cell and not to the more soluble glycosidases. The distribution of the glycosidases between the washes of the cells and the final pellet of bovine RPE cells was examined. The activities of 10 glucosidases in the RPE of the embryonic chick were examined. Neither .beta.-mannosidase nor .beta.-fucosidase activities could be detected in washed bovine RPE cells, although .beta.-mannosidase was detected in RPE of the embryonic chick. The presence of isoenzymes of .beta.-glucuronidase in bovine RPE was indicated. Specificity by .beta.-glucuronidase of bovine RPE for synthetic substrates was observed.