title: A high molecular weight glutamyl endopeptidase and its endogenous inhibitors from cucumber leaves.
abstract: We purified a glutamyl endopeptidase that is a major foliar endopeptidase in cucumber. The endopeptidase had a molecular mass of 400 kDa, consisted of four subunits of 97 kDa, and was inactivated by SH-modifying reagents. Its optimum pH and optimum temperature were 8.0 and 30-37 degrees C, respectively. An internal amino acid sequence of the endopeptidase was highly homologous to a partial sequence of unidentified proteins deduced from genetic information for Arabidopsis thaliana, soybean and rice, but not to the sequences of bacterial glutamyl endopeptidases or animal proteases. Therefore, the unidentified proteins might be glutamyl endopeptidases and be widely distributed only among plant species. The activity of the cucumber glutamyl endopeptidase was inhibited by at least three inhibitors existing in cucumber leaves. One of the inhibitors was a competitive inhibitor of 25 kDa, which did not significantly inhibit commercial endopeptidases derived from animals and microorganisms. This suggests that the cucumber glutamyl endopeptidase might be controlled by endogenous inhibitors in vivo.
authors.affiliation: Laboratory of Plant Biotechnology, Faculty of Agriculture, Tottori University, Koyama, Tottori 680-8553, Japan. yamauchi@muses.tottori-u.ac.jp
authors.forename: Y
authors.initials: Y
authors.lastname: Yamauchi
authors.forename: Y
authors.initials: Y
authors.lastname: Ejiri
authors.forename: T
authors.initials: T
authors.lastname: Sugimoto
authors.forename: K
authors.initials: K
authors.lastname: Sueyoshi
authors.forename: Y
authors.initials: Y
authors.lastname: Oji
authors.forename: K
authors.initials: K
authors.lastname: Tanaka
mesh_terms: D000595:Amino Acid Sequence; D018553:Cucumis sativus / Q000737:chemistry* / Q000201:enzymology; D004795:Enzyme Stability; D006863:Hydrogen-Ion Concentration; D008969:Molecular Sequence Data; D008970:Molecular Weight; D018515:Plant Leaves / Q000737:chemistry* / Q000201:enzymology; D011480:Protease Inhibitors / Q000302:isolation & purification / Q000378:metabolism; D016415:Sequence Alignment; D012697:Serine Endopeptidases / Q000737:chemistry* / Q000302:isolation & purification* / Q000378:metabolism; D013696:Temperature
chemical_list: D011480:Protease Inhibitors; D012697:Serine Endopeptidases; C028344:glutamyl endopeptidase