Abstract
The autolytic activity of various fish(16 species) muscle homogenate in an acidic pH range was measured in the presence of leupeptin and/or pepstatin A. The activity between pH 3 and 5 was inhibited by leupeptin as well as by pepstatin A in all fish examined. Especially, the activities of pointhead flounder Cleisthenes herzensteini, frog flounder Pleuronichthys cornutus, horse mackerel Trachurus japonicus and reticulated emperor Lethrinus semicinctus were inhibited chiefly by leupeptin
The hemoglobin hydrolyzing activities of the crude extract from many fish muscles and livers in the presence of pepstatin A show the maximum activity at pH 4.0, and the activities of fish (53 species) muscles and livers in the presense of pepstatin A and/or leupeptin were measured at pH 4.0. The activities which was not inhibited by pepstatin A but inhibited by leupeptin were detected in almost all fish muscle and liver, and the activities of Pleuronectiformes (flathead flounder Hip-poglossoides dubius, frog flounder, pointhead flounder and bastard halibut Paralichthys olivaceus) were high. It was considered that the activity was due to the cysteine proteinase differing from cathepsin B or L.
