title: Thiol-activated serine proteinases from nymphal hemolymph of the African migratory locust, Locusta migratoria migratorioides.
abstract: Two unique serine proteinase isoenzymes (LmHP-1 and LmHP-2) were isolated from the hemolymph of African migratory locust (Locusta migratoria migratorioides) nymphs. Both have a molecular mass of about 23 kDa and are activated by thiol-reducing agents. PMSF abolishes enzymes activity only after thiol activation, while the cysteine proteinase inhibitors E-64, iodoacetamide, and heavy metals fail to inhibit the thiol-activated enzymes. The N-terminal sequence was determined for the more-abundant LmHP-2 isoenzyme. It exhibits partial homology to that of other insect serine proteinases and similar substrate specificity and inhibition by the synthetic and protein trypsin inhibitors pABA, TLCK, BBI, and STI. The locust trypsins LmHP-1 and LmHP-2 constitute a new category of serine proteases wherein the active site of the enzyme is exposed by thiol activation without cleavage of peptide bonds.
authors.affiliation: Institute of Biochemistry, Food Science and Nutrition, The Hebrew University of Jerusalem, P.O. Box 12, 76100 Rehovot, Israel.
authors.forename: Jacob
authors.initials: J
authors.lastname: Hanzon
authors.forename: Patricia
authors.initials: P
authors.lastname: Smirnoff
authors.forename: Shalom W
authors.initials: SW
authors.lastname: Applebaum
authors.forename: Autar K
authors.initials: AK
authors.lastname: Mattoo
authors.forename: Yehudith
authors.initials: Y
authors.lastname: Birk
mesh_terms: D000349:Africa; D025041:Animal Migration; D000818:Animals; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D004789:Enzyme Activation; D006110:Grasshoppers / Q000201:enzymology*; D006458:Hemolymph / Q000201:enzymology*; D006863:Hydrogen-Ion Concentration; D007460:Iodoacetamide / Q000494:pharmacology; D007930:Leucine / Q000031:analogs & derivatives* / Q000494:pharmacology; D019216:Metals, Heavy / Q000494:pharmacology; D008970:Molecular Weight; D009758:Nymph / Q000201:enzymology; D010664:Phenylmethylsulfonyl Fluoride / Q000494:pharmacology; D020539:Sequence Analysis, Protein; D017386:Sequence Homology, Amino Acid; D012697:Serine Endopeptidases / Q000187:drug effects / Q000302:isolation & purification / Q000378:metabolism*; D015842:Serine Proteinase Inhibitors / Q000494:pharmacology; D013379:Substrate Specificity; D013438:Sulfhydryl Compounds / Q000378:metabolism* / Q000494:pharmacology; D014357:Trypsin / Q000737:chemistry / Q000378:metabolism; D014361:Trypsin Inhibitors / Q000494:pharmacology
chemical_list: D015853:Cysteine Proteinase Inhibitors; D019216:Metals, Heavy; D015842:Serine Proteinase Inhibitors; D013438:Sulfhydryl Compounds; D014361:Trypsin Inhibitors; D010664:Phenylmethylsulfonyl Fluoride; D012697:Serine Endopeptidases; D014357:Trypsin; D007930:Leucine; C024974:E 64; D007460:Iodoacetamide