Partial purification and characterization of proteinases from abdomen part muscle of Antarctic krill.

Abstract

Proteinase activities of abdomen muscle of antarctic krill were very low compared with those in cephalothorax portion. From the badomen muscle extract of antarctic krill Euphausia superba, three types of proteinases were separated by DEAE-cellulose ion exchange chromatography, and designated proteinases I, II and III, respectively. Each proteinases were further purified by gel filtration on Sephadex G-100, DEAE-cellulose (2nd) and hydroxyapatite chromatography. Pro-teinase I hydrolyzed hemoglobin maximally at pH 4.0 and azocasein at pH 5.0. Since proteinase I was inhibited by leupeptin, antipain, monoiodoacetic acid and PCMB, it was classified into thiol proteinase including cathepsin L (EC 3. 4. 22. 15). The molecular weight was determined to be 80, 000, which is higher than that of the muscle of cathepsin L so far reported. Proteinase II hydrolyzed azocasein maximally at pH 6.0. Proteinase II was inhibited by soybean trypsin inhibitor, PMSF and chymostatin. Enzymatic property of proteinase II was similar to that reported for chymotrypsin-like (EC 3. 4. 21. 1) proteinase in krill cephalothorax, but its molecular weight was higher than that of the latter. Since proteinase III hydrolyzed hemoglobin maximally at pH 3.0 and was inhibited by pepstatin, it was a typical acid proteinase.