A novel neutral protease(s) from monkey liver.

A novel neutral protease(s), which is presumably membrane-bound, was found in monkey liver using heat-denatured casein as a substrate and was separated from other major catheptic proteases by successive procedures of gel filtration on Ultrogel AcA 22, solubilization by deoxycholate and gel filtration on Sepharose 6B. The enzyme(s) showed maximal activity at pH 8.0, and was strongly inhibited by DFP and PMSF. Many other reagents tested, including TPCK, TLCK, pCMB, iodoacetic acid, and EDTA, were without marked effect on the activity. Activation of the enzyme(s) by NaCl was not observed.