Automated analyses were used to determine the effect of retinol on the activity of the following proteolytic enzymes: ficin (EC 18.104.22.168), bromelain (EC 3.4.4. 24), trypsin (EC 22.214.171.124.), chymotrypsin A (EC 126.96.36.199), papain (EC 188.8.131.52), clostridiopeptidase A (EC 184.108.40.206), pepsin (EC 220.127.116.11), cathepsin D (EC 3.4.4. 23) from rat-liver and rat-kidney lysosomes and the nonspecific proteolytic enzyme, pronase. Of these proteolytic enzymes only ficin, bromelain, and rat-kidney lysosomal cathepsin D were inhibited significantly by 1×10−4 M retinol.
Some nonproteolytic enzymes not inhibited by retinol were acid phosphatase (EC 18.104.22.168), β-acetylglucosaminidase (EC 22.214.171.124), arylsulfatase (EC 126.96.36.199), and pyruvate kinase (EC 188.8.131.52). The inhibition of cathepsin D varied with the substrate used, being greater with hemoglobin than with ovalbumin or bovine serum albumin. Carotene and retinol inhibited ficin and cathepsin D to similar extents. Retinol inhibition of ficin was partially reversible. These studies of proteolytic enzyme inhibition by retinol serve as a simple model for studying retinol-protein interactions in vitro.
KeywordsRetinol Proteolytic Enzyme Carotene Pyruvate Kinase Chymotrypsin
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