Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.21.4 (trypsin)
 42,187 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The type II transmembrane multidomain serine proteinase MT-SP1/matriptase is highly expressed in many human cancer-derived cell lines and has been implicated in extracellular matrix re-modeling, tumor growth, and metastasis. We have expressed the catalytic domain of MT-SP1 and solved the crystal structures of complexes with benzamidine at 1.3 A and bovine pancreatic trypsin inhibitor at 2.9 A. MT-SP1 exhibits a trypsin-like serine proteinase fold, featuring a unique nine-residue 60-insertion loop that influences interactions with protein substrates. The structure discloses a trypsin-like S1 pocket, a small hydrophobic S2 subsite, and an open negatively charged S4 cavity that favors the binding of basic P3/P4 residues. A complementary charge pattern on the surface opposite the active site cleft suggests a distinct docking of the preceding low density lipoprotein receptor class A domain. The benzamidine crystals possess a freely accessible active site and are hence well suited for soaking small molecules, facilitating the improvement of inhibitors. The crystal structure of the MT-SP1 complex with bovine pancreatic trypsin inhibitor serves as a model for hepatocyte growth factor activator inhibitor 1, the physiological inhibitor of MT-SP1, and suggests determinants for the substrate specificity.
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PMID:Catalytic domain structures of MT-SP1/matriptase, a matrix-degrading transmembrane serine proteinase. 1169 48

Hepatocyte growth factor activator inhibitor type 1 (HAI-1) is a Kunitz-type serine protease inhibitor identified as a strong inhibitor of hepatocyte growth factor (HGF) activator and matriptase. HAI-1 is first produced in a membrane-integrated form with two Kunitz domains in its extracellular region, and subsequent ectodomain shedding releases two major secreted forms, one with a single Kunitz domain and one with two Kunitz domains. To determine the roles of the Kunitz domains in the inhibitory activity of HAI-1 against serine proteases, we constructed various HAI-1 mutant proteins and examined their inhibitory activity against HGF activator and trypsin. The N-terminal Kunitz domain (Kunitz I) had potent inhibitory activity against both HGF activator and trypsin, whereas the C-terminal Kunitz domain (Kunitz II) had only very weak inhibitory activity against HGF activator, although its potency against trypsin was equivalent to that of Kunitz I. These results indicate that Kunitz I is the functional domain of HAI-1 for inhibiting the HGF-converting activity of HGF activator. Furthermore, the presence of two Kunitz domains affected the inhibitory activity of HAI-1 against HGF activator, and it showed a similar, but not additive, level of inhibitory activity against trypsin when compared with that of the individual Kunitz domains. These results suggest that serine protease binding sites of Kunitz I and Kunitz II are located close to each other and that proteolytic processing to generate HAI-1 with only one Kunitz domain regulates the activity of HAI-1.
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PMID:Functional characterization of Kunitz domains in hepatocyte growth factor activator inhibitor type 1. 1180 18

Hepatocyte growth factor activator (HGFA) is a serine protease that converts hepatocyte growth factor (HGF) into its active form. When activated HGF binds its cognate receptor Met, cellular signals lead to cell growth, differentiation, and migration, activities which promote tissue regeneration in liver, kidney and skin. Intervention in the conversion of HGF to its active form has the potential to provide therapeutic benefit where HGF/Met activity is associated with tumorigenesis. To help identify ways to moderate HGF/Met effects, we have determined the molecular structure of the protease domain of HGFA. The structure we determined, at 2.7 A resolution, with no pseudo-substrate or inhibitor bound is characterized by an unconventional conformation of key residues in the enzyme active site. In order to find whether this apparently non-enzymatically competent arrangement would persist in the presence of a strongly-interacting inhibitor, we also have determined, at 2.6 A resolution, the X-ray structure of HGFA complexed with the first Kunitz domain (KD1) from the physiological inhibitor hepatocyte growth factor activator inhibitor 1B (HAI-1B). In this complex we observe a rearranged substrate binding cleft that closely mirrors the cleft of other serine proteases, suggesting an extreme conformational dynamism. We also characterize the inhibition of 16 serine proteases by KD1, finding that the previously reported enzyme specificity of the intact extracellular region of HAI-1B resides in KD1 alone. We find that HGFA, matriptase, hepsin, plasma kallikrein and trypsin are potently inhibited, and use the complex structure to rationalize the structural basis of these results.
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PMID:Conformational lability in serine protease active sites: structures of hepatocyte growth factor activator (HGFA) alone and with the inhibitory domain from HGFA inhibitor-1B. 1571 85

Hepatocyte growth factor activator inhibitor type 1 (HAI-1) is a membrane-bound serine proteinase inhibitor having two extracellular Kunitz-type proteinase inhibitor domains (KD) namely KD-1 and KD-2. It efficiently inhibits hepatocyte growth factor activator, matriptase, hepsin, prostasin and trypsin. We have previously reported that the expression of HAI-1 suppresses the in vitro invasive capability of human glioblastoma cells. In this study we examined the role of each KD in the anti-invasive effect of HAI-1. Engineered over-expression of the mature membrane-form HAI-1 suppressed in vitro fibrin gel invasion of two human glioblastoma cell lines, U251 and YKG-1. The migratory activity on type IV collagen was also suppressed by the HAI-1 expression. These effects were not affected by the deletion of intracytoplasmic domain of HAI-1. A truncated secreted form of HAI-1 also suppressed in vitro invasion of the cells, indicating that the extracellular portion of HAI-1 was responsible for the anti-invasive effect. To determine the roles of each KD in the anti-invasive effect of HAI-1 in vitro, we constructed expression plasmids for HAI-1 with or without mutation at the P1 position of the reactive site of each KD. The results revealed that the proteinase inhibitor activity of N-terminal KD (KD-1) is responsible for the anti-invasion effect of HAI-1.
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PMID:Roles of Kunitz domains in the anti-invasive effect of hepatocyte growth factor activator inhibitor type 1 in human glioblastoma cells. 1794 49

Hepatocyte growth factor activator inhibitor-1 (HAI)-1 is an epithelial Kunitz-type transmembrane serine protease inhibitor that is encoded by the SPINT1 gene. HAI-1 displays potent inhibitory activity toward a large number of trypsin-like serine proteases. HAI-1 was recently shown to play an essential role in postnatal epithelial homeostasis. Thus, Spint1-deficient mice were found to display severe growth retardation and are unable to survive beyond postnatal day 16. The mice present histologically with overt hyperkeratosis of the forestomach, hyperkeratosis and acanthosis of the epidermis, and hypotrichosis associated with abnormal cuticle development. In this study, we show that loss of inhibition of a proteolytic pathway that is dependent on the type II transmembrane serine protease, matriptase, underlies the detrimental effects of postnatal Spint1 deficiency. Matriptase and HAI-1 precisely co-localize in all tissues that are affected by the Spint1 disruption. Spint1-deficient mice that have low matriptase levels, caused by a hypomorphic mutation in the St14 gene that encodes matriptase, not only survived the neonatal period but were healthy and displayed normal long-term survival. Furthermore, a detailed histological analysis of neonatal, young adult, as well as aged mice did not reveal any abnormalities in Spint1-deficent mice that have low matriptase levels. This study identifies matriptase suppression as an essential function of HAI-1 in postnatal tissue homeostasis.
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PMID:Loss of matriptase suppression underlies spint1 mutation-associated ichthyosis and postnatal lethality. 1938 29