Selective presence of acid hydrolases in the interphotoreceptor matrix

  • Adler A
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Adler and Martin (1983, Curr. Eye Res. 2, 359-66) found cathepsin D to be present in crude preparations of bovine interphotoreceptor matrix (IPM). The purpose of the present study was to determine, by investigating several acid hydrolases in purer IPM samples, whether hydrolytic enzymes abundant in RPE lysosomes were present also as normal components of the IPM. IPM was prepared from bovine eyes by the introduction of a small bleb of buffer between the neural retina and the RPE. These IPM samples were free from significant contamination by surrounding tissues; they contained IRBP as their only major protein, and had negligible amounts of lactate dehydrogenase and ROS-specific proteins. Most acid hydrolases were assayed fluorometrically by measuring the 4-methylumbelliferone released upon hydrolysis of appropriate derivatives; the substrate for cathepsin was hemoglobin. The amounts of the enzymes found in the IPM were far from uniform and could not be correlated with enzyme activities in either RPE or retina homogenates. The hydrolases in the IPM varied in amount from β-galactosidase (28% of the RPE level), through N-acetyl-β-glucosaminidase (20%), α-fucosidase (15%), β-glucuronidase (12%), α-glucosidase (8%), cathepsin D (7%), α-mannosidase (7%), down to β-glucosidase, acid phosphatase, and acid lipase (trace amounts,

Author-supplied keywords

  • RPE secretions
  • extracellular acid hydrolases
  • interphotoreceptor matrix
  • lysosomal enzymes

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  • Alice J. Adler

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