Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.4.21.1 (chymotrypsin)
 10,938 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A serine proteinase inhibitor isolated from Leucaena leucocephala seeds (LlTI) was purified to homogeneity by acetone fractionation, ion exchange chromatography, gel filtration and reverse phase chromatography (HPLC). SDS-PAGE indicated a protein with M(r) 20000 and two polypeptide chains (alpha-chain, M(r) 15000, and beta-chain, M(r) 5000), the sequence being determined by automatic Edman degradation and by mass spectroscopy. LlTI is a 174 amino acid residue protein which shows high homology to plant Kunitz inhibitors, especially those double chain proteins purified from the Mimosoideae subfamily. LlTI inhibits plasmin (K(i) 3.2 x 10(-10) M), human plasma kallikrein (K(i) 6.3 x 10(-9) M), trypsin (K(i) 2.5 x 10(-8) M) and chymotrypsin (K(i) 1.4 x 10(-8) M). Factor XIIa activity is inhibited but K(i) was not determined, and factor Xa, tissue kallikrein and thrombin are not inhibited by LlTI. The action of LlTI on enzymes that participate in the blood clotting extrinsic pathway is confirmed by the prolongation of activated partial thromboplastin time, used as clotting time assay. The inhibition of the fibrinolytic activity of plasmin was confirmed on the hydrolysis of fibrin plates. LlTI inhibits kinin release from high molecular weight kininogen by human plasma kallikrein in vitro and, administered intravenously, causes a decrease in paw edema induced by carrageenin or heat in male Wistar rats. In addition, lower concentrations of bradykinin were found in limb perfusion fluids of LlTI-treated rats.
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PMID:Leucaena leucocephala serine proteinase inhibitor: primary structure and action on blood coagulation, kinin release and rat paw edema. 1070 49

Kallistatin is a serpin with a unique P1 Phe, which confers an excellent inhibitory specificity toward tissue kallikrein. In this study, we investigated the P3-P2-P1 residues (residues 386-388) of human kallistatin in determining inhibitory specificity toward human tissue kallikrein by site-directed mutagenesis and molecular modeling. Human kallistatin mutants with 19 different amino acid substitutions at each P1, P2, or P3 residue were created and purified to compare their kallikrein binding activity. Complex formation assay showed that P1 Arg, P1 Phe (wild type), P1 Lys, P1 Tyr, P1 Met, and P1 Leu display significant binding activity with tissue kallikrein among the P1 variants. Kinetic analysis showed the inhibitory activities of the P1 mutants toward tissue kallikrein in the order of P1 Arg > P1 Phe > P1 Lys >/= P1 Tyr > P1 Leu >/= P1 Met. P1 Phe displays a better selectivity for human tissue kallikrein than P1 Arg, since P1 Arg also inhibits several other serine proteinases. Heparin distinguishes the inhibitory specificity of kallistatin toward kallikrein versus chymotrypsin. For the P2 and P3 variants, the mutants with hydrophobic and bulky amino acids at P2 and basic amino acids at P3 display better binding activity with tissue kallikrein. The inhibitory activities of these mutants toward tissue kallikrein are in the order of P2 Phe (wild type) > P2 Leu > P2 Trp > P2 Met and P3 Arg > P3 Lys (wild type). Molecular modeling of the reactive center loop of kallistatin bound to the reactive crevice of tissue kallikrein indicated that the P2 residue required a long and bulky hydrophobic side chain to reach and fill the hydrophobic S2 cleft generated by Tyr(99) and Trp(219) of tissue kallikrein. Basic amino acids at P3 could stabilize complex formation by forming electrostatic interaction with Asp(98J) and hydrogen bond with Gln(174) of tissue kallikrein. Our results indicate that tissue kallikrein is a specific target proteinase for kallistatin.
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PMID:Roles of the P1, P2, and P3 residues in determining inhibitory specificity of kallistatin toward human tissue kallikrein. 1099 87

The medicinal leech Hirudo medicinalis produces various types of proteinase inhibitors: bdellins (inhibitors of trypsin, plasmin, and acrosin), hirustasin (inhibitor of tissue kallikrein, trypsin, alpha-chymotrypsin, and granulocyte cathepsin G), tryptase inhibitor, eglins (inhibitors of alpha-chymotrypsin, subtilisin, and chymasin and the granulocyte proteinases elastase and cathepsin G), inhibitor of factor Xa, hirudin (thrombin inhibitor), inhibitor of carboxypeptidase, and inhibitor of complement component C1s. This review summarizes data on their primary and tertiary structures, action mechanisms, and biological activities.
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PMID:Proteinase inhibitors from the medicinal leech Hirudo medicinalis. 1156 48

The three-dimensional structure of a novel Kunitz (STI) family member, an inhibitor purified from Delonix regia seeds (DrTI), was solved by molecular replacement method and refined, respectively, to R(factor) and R(free) values of 21.5% and 25.3% at 1.75A resolution. The structure has a classical beta-trefoil fold, however, differently from canonical Kunitz type (STI) inhibitors, its reactive site loop has an insertion of one residue, Glu68, between the residues P1 and P2. Surprisingly, DrTI is an effective inhibitor of trypsin and human plasma kallikrein, but not of chymotrypsin and tissue kallikrein. Putative structural grounds of such specificity are discussed.
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PMID:Crystal structure of the Kunitz (STI)-type inhibitor from Delonix regia seeds. 1465 16

Kallikreins are secreted serine proteases with important roles in human physiology. Human plasma kallikrein, encoded by the KLKB1 gene on locus 4q34-35, functions in the blood coagulation pathway, and in regulating blood pressure. The human tissue kallikrein and kallikrein-related peptidases (KLKs) have diverse expression patterns and physiological roles, including cancer-related processes such as cell growth regulation, angiogenesis, invasion, and metastasis. Prostate-specific antigen (PSA), the product of the KLK3 gene, is the most widely used biomarker in clinical practice today. A total of 15 KLKs are encoded by the largest contiguous cluster of protease genes in the human genome (19q13.3-13.4), which makes them ideal for evolutionary analysis of gene duplication events. Previous studies on the evolution of KLKs have traced mammalian homologs as well as a probable early origin of the family in aves, amphibia and reptilia. The aim of this study was to address the evolutionary and functional relationships between tissue KLKs and plasma kallikrein, and to examine the evolution of alternative splicing isoforms. Sequences of plasma and tissue kallikreins and their alternative transcripts were collected from the NCBI and Ensembl databases, and comprehensive phylogenetic analysis was performed by Bayesian as well as maximum likelihood methods. Plasma and tissue kallikreins exhibit high sequence similarity in the trypsin domain (>50%). Phylogenetic analysis indicates an early divergence of KLKB1, which groups closely with plasminogen, chymotrypsin, and complement factor D (CFD), in a monophyletic group distinct from trypsin and the tissue KLKs. Reconstruction of the earliest events leading to the diversification of the tissue KLKs is not well resolved, indicating rapid expansion in mammals. Alternative transcripts of each KLK gene show species-specific divergence, while examination of sequence conservation indicates that many annotated human KLK isoforms are missing the catalytic triad that is crucial for protease activity.
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PMID:Evolution of the plasma and tissue kallikreins, and their alternative splicing isoforms. 2387 99


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