|Budget Amount *help
¥2,000,000 (Direct Cost : ¥2,000,000)
Fiscal Year 1993 : ¥800,000 (Direct Cost : ¥800,000)
Fiscal Year 1992 : ¥1,200,000 (Direct Cost : ¥1,200,000)
Animal cysteine proteinase inhibitors form so called "Cystatin Superfamily", which coprises at least three families : I (the stefin family), II (the cystatin family) and III (the kininogen family). These proteinase inhibitors are proposed to be derived from a common ancestor and their physiological functions seem to regulate protein metabolisms or to protect cells against unfavorable proteolysis by intracellular and external cysteine proteinase.
Human cystatins of family II are secretory proteins (Mw = 14.5kDa) with two disulfide bonds. five molecular species of htis class, cystatins S, SA, SN, C, and D have been identified by us and others. they are produced in a variety of tissues by the differential expression of members from the cystaion gene family on chromosome 20 (pll.2). At present, seven cystatin loci are clarified by us and others : CST1 (cystatin SN gene), CST2 (cystatin SA gene), CST3 (cystatin C gene), CST4 (cystatin S gene), CST5 (cystatin D gene), CSTP1 (pseudogene) and CSTP2 (pseudogene).
Production of large amount of the cystatins and their variants allows us not only to study the structural and functional relationships of cystations but also to investigate the therapeutic potential of the proteinase inhibitors. In this study, we established an E.coli system enabling a high level expression and secretion of salivary (S-type) cystatins. The amino terminal 10 amino acid sequence of recombinant cystatin S thus produced was to be SSSKEENRII-. The recombinant cystatin S inhibited ficin, papain and cathepsin C, but cathepsin B as well as the natural one.