2024-03-28T14:44:35Zhttps://eprints.lib.hokudai.ac.jp/dspace-oai/requestoai:eprints.lib.hokudai.ac.jp:2115/430642022-11-17T02:08:08Zhdl_2115_20049hdl_2115_141Three types of proteinases in Japanese common squid Todarodes pacificus hepatopancreas as studied by using carp myofibrils as substrateTian, YuanyongUmezawa, EmiDuan, RuiKonno, KunihikoCysteine-proteinaseDenaturationHepatopancreasJapanese common squidMyofibrilsProteinase664Three types of proteinases, namely cysteine-, metallo-, and serine-proteinases, were found in squid hepatopancreas by studying the inhibition spectra using carp myofibril as substrate. The cysteine-, metallo-, and serine-types showed the highest activities at 50℃, 35℃, and 40℃, respectively. The optimal pHs were pH 5, pH 7, and pH 9 for the cysteine-, metallo-, and serine-types, respectively. When assayed at 20℃ and pH 7.5, the metallo-type showed the highest activity. The metallo-type was characterized by a high selectivity in the digestion of myosin. Among the three enzymes, the cysteine-type was found to be the most stable against thermal and acid treatments. Heat treated myofibrils were more susceptible to cysteine- and serine-types, but less susceptible to the metallo-type. Acid treatment of myofibrils also enhanced the digestibility by cysteine type. The results indicated that the cysteine-type seemed to be the most suitable enzyme to produce peptides from denatured myofibrils by their random digestion.Springer JapanJournal Articleapplication/pdfhttp://hdl.handle.net/2115/43064https://eprints.lib.hokudai.ac.jp/dspace/bitstream/2115/43064/1/FS76-2_365-373.pdf0919-9268Fisheries Science7623653732010-03enginfo:doi/10.1007/s12562-009-0206-xThe original publication is available at www.springerlink.comauthor