title: Amino-acid-sequence determination and biological activity of cytin, a naturally occurring specific chymotrypsin inhibitor from the leech Theromyzon tessulatum.
abstract: We purified a chymotrypsin inhibitor, designated cytin, from the rhynchobdellid leech Theromyzon tessulatum. This 7.4-kDa peptide was purified to apparent homogeneity by gel-permeation and anion-exchange chromatographies, followed by reverse-phase HPLC. The structure of cytin was determined by reduction, S-beta-pyridilethylation, automated Edman degradation, and electrospray mass spectrometry. Cytin is formed by the association of two protein chains, which are linked by a disulfide bridge. Chain A consists of 43 and chain B of 22 amino acid residues. Chain B exhibits 40-63% sequence similarity with the N-terminal sequences of subtilisin/chymotrypsin inhibitors isolated from barley seeds. Cytin inhibited chymotrypsin (Ki 600 pM) and weakly inhibited trypsin (Ki 350 nM). This chymotrypsin inhibitor, in contrast to others isolated from leeches, does not inhibit elastase or cathepsin G. Furthermore, cytin (10 microM) significantly diminishes the level of human granulocyte and monocyte activation induced by lipopolysaccharide (1 U/ml) in a manner similar to that of aprotinin. These data indicate that this chymotrypsin inhibitor may be biomedically significant.
authors.affiliation: Laboratoire d'Endocrinologie des Annélides, Université des Sciences et Technologies de Lille, Villeneuve d'Ascq, France.
authors.forename: V
authors.initials: V
authors.lastname: Chopin
authors.forename: T V
authors.initials: TV
authors.lastname: Bilfinger
authors.forename: G B
authors.initials: GB
authors.lastname: Stefano
authors.forename: I
authors.initials: I
authors.lastname: Matias
authors.forename: M
authors.initials: M
authors.lastname: Salzet
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D007611:Aprotinin / Q000494:pharmacology; D002851:Chromatography, High Pressure Liquid; D002918:Chymotrypsin / Q000037:antagonists & inhibitors*; D019075:Electrophoresis, Capillary; D006098:Granulocytes / Q000187:drug effects / Q000502:physiology; D006801:Humans; D007865:Leeches / Q000737:chemistry*; D008070:Lipopolysaccharides / Q000037:antagonists & inhibitors / Q000494:pharmacology; D013058:Mass Spectrometry; D008969:Molecular Sequence Data; D009000:Monocytes / Q000187:drug effects / Q000502:physiology; D010455:Peptides / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology; D011506:Proteins / Q000737:chemistry* / Q000302:isolation & purification / Q000494:pharmacology; D017421:Sequence Analysis; D015842:Serine Proteinase Inhibitors / Q000737:chemistry* / Q000302:isolation & purification / Q000494:pharmacology; D013379:Substrate Specificity
chemical_list: D008070:Lipopolysaccharides; D010455:Peptides; D011506:Proteins; D015842:Serine Proteinase Inhibitors; C109591:cytin protein, Thereomyzon tessulatum; D007611:Aprotinin; D002918:Chymotrypsin