A cysteine-activated protease isolated from Todarodes pacificus squid degrades collagen below its denaturation temperature.

Collagen purified from the mantle muscle of the Japanese common squid, Todarodes pacificus, showed autodegradation during incubation under acidic conditions at 25°C, without the addition of exogenous enzymes. This suggests that the collagenolytic proteases bind to collagen tightly through the steps of collagen preparation. Collagenolytic activity also was detected in a crude extract of mantle muscle, and leupeptin and E-64 were observed to inhibit collagenolytic activity within the collagen fraction and muscle extract. We purified these collagenolytic cysteine proteases by leupeptin column chromatography and cellulose acetate membrane electrophoresis. Optimal enzymatic activity was observed at pH 3.5, and collagenolytic activity was completely suppressed at neutral or alkaline pH. The purified enzymes were 28 kDa and 25 kDa in size, and both had gelatinolytic activity, as detected by gelatin zymography, and cut the specific site of denatured collagen α chain. The purified enzymes degraded squid collagen a...