title: Involvement of cathepsin B- and L-like proteinases in silk gland histolysis during metamorphosis of Bombyx mori.
abstract: To identify proteinases involved in programmed cell death of the silk glands of Bombyx mori, we measured enzyme activities in silk gland homogenates. Several peptidyl-4-methylcoumaryl-7-amides (MCAs) and bovine hemoglobin were used as substrates in the presence and absence of proteinase inhibitors. The hydrolysis of t-butyloxycarbonyl-Phe-Ser-Arg-MCA (Boc-FSR-MCA), benzyloxy-carbonyl-Phe-Arg-MCA (Z-FR-MCA), and Z-Arg-Arg-MCA (Z-RR-MCA) was optimal at pH 5.5, 5.0, and 5.5, respectively. It was stimulated by the sulfhydryl compounds or EDTA and inhibited by both cysteine proteinase inhibitors and a cathepsin B-specific inhibitor, l-3-trans-(propyl-carbamoyl)oxirane-2-carbonyl)-L-isoleucyl-L-prolin (CA-074). The hemoglobin hydrolysis at the optimum pH 3.5 was inactivated by cysteine proteinase inhibitors, but stimulated slightly by pepstatin. The cleavage of Arg-MCA (R-MCA) and Leu-MCA (L-MCA) at optimum pH of 7.0 was strongly inhibited by an aminopeptidase inhibitor, puromycin, and by sulfhydryl compounds. The Boc-FSR-MCA, Z-FR-MCA, Z-RR-MCA, and hemoglobin hydrolyzing activities increased in the silk glands dramatically after cocoon formation, while the R-MCA and L-MCA cleaving activities declined. The results strongly suggest the involvement of cathepsin B- and cathepsin L-like proteinases in the histolysis of the silk gland during metamorphosis.
authors.affiliation: Department of Applied Biological Science, College of Bioresource Sciences, Nihon University, 1866 Kameino, Fujisawa-shi, Kanagawa, 252-8510, Japan. chang@brs.nihon-u.ac.jp
authors.forename: H
authors.initials: H
authors.lastname: Shiba
authors.forename: D
authors.initials: D
authors.lastname: Uchida
authors.forename: H
authors.initials: H
authors.lastname: Kobayashi
authors.forename: M
authors.initials: M
authors.lastname: Natori
mesh_terms: D000818:Animals; D012831:Bombyx / Q000201:enzymology* / Q000254:growth & development*; D002401:Cathepsin B / Q000378:metabolism*; D056668:Cathepsin L; D002403:Cathepsins / Q000378:metabolism*; D002417:Cattle; D003546:Cysteine Endopeptidases; D010450:Endopeptidases; D005088:Exocrine Glands / Q000201:enzymology / Q000254:growth & development; D006454:Hemoglobins / Q000378:metabolism; D006868:Hydrolysis; D066298:In Vitro Techniques; D019476:Insect Proteins / Q000378:metabolism; D007700:Kinetics; D008675:Metamorphosis, Biological; D011480:Protease Inhibitors / Q000494:pharmacology; D047011:Silk; D013379:Substrate Specificity
chemical_list: D006454:Hemoglobins; D019476:Insect Proteins; D011480:Protease Inhibitors; D047011:Silk; D002403:Cathepsins; D010450:Endopeptidases; D003546:Cysteine Endopeptidases; D002401:Cathepsin B; D056668:Cathepsin L