Partial purification of cathepsin B in the bovine ciliary body and iris

Cathepsin B in the bovine ciliary body and iris was studied biochemically using alpha-N-benzoyl-D,L-arginine-2-naphthylamide as substrate. The enzyme was purified to 210-fold from the autolyzed extract. The partially purified enzyme had a pH optimum at 6.0 and a molecular weight of 27,000. The apparent Km value for the substrate was 1.6 mM. The enzyme was activated by disodium ethylenediamine tetraacetate, cysteine, and dithiothreitol. The enzyme activity was inhibited strongly by leupeptin and partially by hyaluronate and chondroitin sulfate A.