title: Isolation and characterization of a trypsin inhibitor from the skin secretions of Kaloula pulchra hainana.
abstract: Amphibian skin secretions contain many bioactive compounds. A trypsin inhibitor termed KPHTI was purified from the skin secretions of frog Kaloula pulchra hainana by successive ion-exchange and gel-filtration chromatography. KPHTI is a single chain glycoprotein, with an apparent molecular weight of 23 kDa in SDS-PAGE. It is a competitive inhibitor and effectively inhibits trypsin catalytic activity on peptide substrate with the inhibitor constant (K(i)) value of 27 nM. KPHTI shows no inhibitory effect on chymotrypsin, thrombin, elastase, and subtilisin. The N-terminal sequence of KPHTI is DHEVTS, which shows no similarity with other known trypsin inhibitors. DTT apparently affected the inhibitory activity of KPHTI. But it was not sensitive to temperature and pH range, which suggested that it possessed stable trypsin inhibitory activity in natural environment, and maybe play an important role in against predators.
authors.affiliation: Key Laboratory of Tropic Biological Resources, Minister of Education, Haikou 570228, PR. China. yingxiazhang@hotmail.com
authors.forename: Yingxia
authors.initials: Y
authors.lastname: Zhang
authors.forename: Manchuriga
authors.initials: M
authors.lastname: Wang
authors.forename: Shuangshuang
authors.initials: S
authors.lastname: Wei
mesh_terms: D000818:Animals; D001001:Anura; D002850:Chromatography, Gel; D002852:Chromatography, Ion Exchange; D004229:Dithiothreitol / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D055550:Protein Stability; D012867:Skin / Q000737:chemistry* / Q000378:metabolism; D013696:Temperature; D014361:Trypsin Inhibitors / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism
chemical_list: D014361:Trypsin Inhibitors; D004229:Dithiothreitol