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)

Isomerization of 5-pregnene-3,20-dione to progesterone by human placental microsomes was stimulated by NAD and NADH. Concomitant oxidation or reduction of nucleotide was not detected based on absorbance at 340 nm. Concentrations giving half-maximum activity were 0.76 microM for NADH and 24.0 microM for NAD. Vmax values with 9.28 microM 5-pregnene-3,20-dione were 22.0 nmol/min/mg protein with NADH and 65.8 nmol/min/mg protein with NAD. When isomerase was assayed as a function of 5-pregnene-3,20-dione concentration, NAD increased Vmax but had no effect on the Km value for steroid. NADP, NADPH, acetylpyridine NAD and deamino NAD did not activate nor did they compete with NAD. Exposure of microsomes to trypsin, phospholipase A2 or phospholipase C resulted in the loss of isomerase activity. Approximately 30% of the initial activity was recovered after detergent solubilization of microsomes. Hydrogen peroxide did not affect activation by NAD. The data are consistent with nucleotide enhancement of a step in the isomerization reaction other than substrate binding.
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PMID:Activation of human placental 5-pregnene-3,20-dione isomerase activity by pyridine nucleotides. 337 61

The effects of exogenously added phospholipase A2 (PLA2) and its hydrolytic products in isolated bullfrog sciatic nerve were investigated. Nerves were pretreated for 3 h with a dose of trypsin which did not affect conduction in order to enhance penetration of the added agents. Treatment of nerves with beta-glucosidase, neuraminidase or chymotrypsin had no effect on conduction. Whereas incubation of the nerves with normal Ringers for 2 h had no significant effect on conduction, incubation with PLA2 in Ringers caused decrements in the height of the compound action potential in a dose-related manner. In addition, incubation of the nerves with 10 mg/ml lysolecithin, arachidonic acid, or docosahexaenoic acid caused marked decrements in the height of the compound action potential. Electron microscopic analysis of nerves after each treatment which caused conduction block revealed varying levels of myelin damage. Although myelin was damaged at the paranodal and/or internodal region, depending on the agents used, the axonal membrane appeared to be intact at the ultrastructural level. It was concluded that the block in conduction resulting from PLA2 was due to the formation of lysolecithin and long chain polyunsaturated fatty acids.
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PMID:Mechanism of phospholipase A2-induced conduction block in bullfrog sciatic nerve. I. Electrophysiology and morphology. 348 69

Classical techniques for studying modulations of microvascular permeability have a time resolution of minutes. A newly developed method allows continuous measurement of the electrical resistance of the microvascular membrane in vivo (Olesen & Crone 1983). The technique exploits microelectrodes impaled into the vascular lumen and is based on cable analysis of the vessel. It was applied to venules on the surface of the frog brain to test the effect on microvascular permeability of a wide variety of substances. The following agents increased ionic permeability reversibly within seconds: 5-hydroxytryptamine, bradykinin, ATP, ADP, AMP, phospholipase A2, arachidonic acid, leukotriene C4, oxygen-derived free radicals, ionophore A23187, and unbound Evans blue dye. An irreversible permeability increase was induced by protamine sulphate, neuraminidase, trypsin, melittin, and snake venoms from Crotalus durissus terrificus and Bothrops atrox. The following substances were without effect within an administration period of 5 min: histamine, epinephrine, putrescine, angiotensin II, vasoactive intestinal polypeptide (VIP), substance P, neurotensin, vasopressin, adenosine, PGE2, PGF2 alpha, prostacyclin (PGI2), leukotriene B4, albumin, heparin, plant cytokinins, hyaluronidase, thrombin, wasp venom. Variations in pH between 5.1 and 8.6 did not change permeability. Three conclusions are drawn from the observations: (1) the permeability of cerebral microvessels can be modulated by specific agents, (2) the agents induced changes in the endothelium within a few seconds, and (3) the rapid permeability increase induced by inflammatory mediators was less than two-fold and reversible within minutes.
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PMID:Substances that rapidly augment ionic conductance of endothelium in cerebral venules. 348 16

The amino acid sequence of phospholipase A2 from the venom of Trimeresurus flavoviridis (the Habu snake) was determined. The enzyme subunit has a molecular weight of 13,764 and consists of a single polypeptide chain of 122 amino acids and seven disulfide bonds. The fragmentation was conducted by digesting the reduced and S-carboxymethylated derivative of the protein with Achromobacter protease I, chymotrypsin, and trypsin, respectively. Achromobacter protease I peptides were used for alignment and to establish overlaps over chymotryptic and tryptic peptides. The automated Edman degradation of the S-carboxymethylated protein, which was extended to the N-terminal 30 amino acid residues, supplemented the deletions found with the enzymatic peptides alone. T. flavoviridis phospholipase A2 was found to be highly (65-67%) homologous in sequence to the enzymes from T. okinavensis, Crotalus adamanteus, and Crotalus atrox (viperid family) and less (35-44%) homologous to those from elapid snakes and mammalian pancreas. The T. flavoviridis enzyme appears to be similar in secondary structure composition to the C. atrox enzyme.
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PMID:Amino acid sequence of Trimeresurus flavoviridis phospholipase A2. 351 93

The structure of the potent inflammatory mediator, platelet-activating factor, is 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine (AGEPC, PAF-acether). Human sera contain an acid labile factor (ALF) that is a Ca+2-independent 2-acylhydrolase-specific for AGEPC and AGEPC-like molecules. The enzyme functions by catalytically removing the sn-2 acetyl moiety from AGEPC, producing the biologically inactive sn-2 hydroxy form or 2-lyso-GEPC. Incubation of ALF with sn-2 acyl PAF analogs indicated that the enzyme hydrolyzes the sn-2 fatty acid only if the chain length is five carbons or less, the sn-1 position fatty acid length is greater than 10 carbon units, and at least one methyl group is present on the terminal amine of the choline group. The enzyme was active with either an ether or ester linkage at the sn-1 position. ALF is inactivated by heating to 65 degrees C for 30 min. It is pronase and trypsin sensitive but resistant to papain and papain with dithiothreitol. Further characteristics of human ALF indicated a broad pH range of activity with an optimum of pH 6.2 and an isoelectric point of 6.2 to 6.7. The specificity and Ca+2 independence of human ALF sets it apart from phospholipase A2. It is proposed that human ALF be called human serum PAF-acylhydrolase to distinguish it from other hydrolases currently known to exist.
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PMID:Substrate specificity and partial characterization of the PAF-acylhydrolase in human serum that rapidly inactivates platelet-activating factor. 351 60

A basic (pI = 10.2) phospholipase A2 of the venom of the snake Agkistrodon halys blomhoffii is one of a few phospholipases A2 capable of hydrolyzing the phospholipids of Escherichia coli killed by a bactericidal protein purified from human or rabbit neutrophil granules. We have shown that modification of as many as 4 mol of lysine per mole of the phospholipase A2, either by carbamylation or by reductive methylation [Forst, S., Weiss, J., & Elsbach, P. (1982) J. Biol. Chem. 257, 14055-14057], had no effect on catalytic activity toward extracted E. coli phospholipids or the phospholipids of autoclaved E. coli. In contrast, modification of 1 mol of lysine per mole of enzyme substantially reduced activity toward the phospholipids of E. coli killed by the neutrophil protein. To explore further the role of lysines in the function of this phospholipase A2, we determined the amino acid sequence of the enzyme and the incorporation of [14C]cyanate into individual lysines when, on average, 1 lysine per molecule of enzyme had been carbamylated. After incorporation of approximately 1 mol of [14C]cyanate per mole of protein, the phospholipase A2 was reduced, alkylated, and exhaustively carbamylated with unlabeled cyanate. The amino acid sequence was determined of the NH2-terminal 33 amino acids of the holoprotein and of peptides isolated after digestion with trypsin and Staphylococcus aureus V-8 protease. The protein contains 122 amino acid residues, 17 of which are lysines. The NH2-terminal region is unique among more than 30 phospholipases A2 previously sequenced because of its high content of basic residues (His-1, Arg-6, and Lys-7, -10, -11, and -15).(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Amino acid sequence of a basic Agkistrodon halys blomhoffii phospholipase A2. Possible role of NH2-terminal lysines in action on phospholipids of Escherichia coli. 353 Mar 22

Homogenates of rat adipocytes and plasma membranes thereof were shown by radioimmunoassay to contain immunoreactive glandular kallikrein. On the basis of the hydrolysis of D-Val-Leu-Arg-p-nitroanilide, the kallikrein-like enzyme associated with the plasma membranes was found not to be stimulated by prior incubation with melittin or phospholipase A2. However, pre-incubation of the membrane preparation with trypsin did increase the activity of the enzyme. Furthermore, activation could also be achieved by incubating the plasma membranes with insulin at a dose that stimulated glucose uptake into intact adipocytes. On the other hand, incubation with insulin at a dose that did not increase glucose uptake into rat adipocytes was ineffective in activating the kallikrein-like enzyme.
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PMID:Initial observations of a kallikrein-like enzyme associated with the plasma membranes of rat adipocytes. 354 19

Antibodies prepared against the phospholipase A2 stimulatory peptide melittin were used to identify and isolate a novel mammalian protein with similar functional and antigenic properties. The mammalian protein of Mr 28,000 was isolated from cell sonicates by high performance immunoaffinity chromatography and size exclusion chromatography. This stimulatory protein was stable for several months when frozen at -70 degrees C. The purified protein selectively stimulated phospholipase A2 when phosphatidylcholine was used as a substrate but had no effect on phospholipase A2 activity when phosphatidylethanolamine was used as a substrate. Furthermore, this protein had no effect on phospholipase C activity or on pancreatic or snake venom phospholipase A2. The stimulatory activity was unaffected by RNase or DNase treatment. However, boiling or trypsin digestion inactivated the phospholipase stimulatory activity. The mechanism of phospholipase A2 stimulation appeared to result from an increase in the apparent Vmax of the enzyme.
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PMID:Identification and isolation of a mammalian protein which is antigenically and functionally related to the phospholipase A2 stimulatory peptide melittin. 354 34

The binding ability of Cl. botulinum neurotoxin to synaptosomes upon treatment with various enzymes (neuraminidase, trypsin, and beta-bungarotoxin containing phospholipase A2 activity) was studied. When synaptosomes were treated with neuraminidase, their ability to bind toxin decreased; trypsin and beta-bungarotoxin had slightly week or no effect. The decrease in toxin-binding ability of synaptosomes was paralleled by a release of sialic acid from the synaptosomes by the neuraminidase treatment. The toxin-binding ability of synaptosomes treated with neuraminidase was lower than untreated ones at a high concentration of sodium chloride. The binding of the toxin to synaptosomes occurred at least at the two types of structural sites, one site which contained sialic acid, and other site which was sensitive to high ionic strength. It may be possible that another binding state except these is present at the synapse.
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PMID:Binding ability of Clostridium botulinum neurotoxin to the synaptosome upon treatment of various kinds of the enzymes. 356 63

Lipstatin, a new and very potent inhibitor of pancreatic lipase (the key enzyme of intestinal fat digestion) was isolated from Streptomyces toxytricini. Lipstatin contains a beta-lactone structure that probably accounts for the irreversible lipase inhibition. The IC50 of lipstatin for pancreatic lipase is 0.14 microM. In mice triolein absorption was dose-dependently inhibited by lipstatin, whereas oleic acid was absorbed normally. Other pancreatic enzymes, such as phospholipase A2 and trypsin, were not inhibited even at an inhibitor concentration of 200 microM.
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PMID:Lipstatin, an inhibitor of pancreatic lipase, produced by Streptomyces toxytricini. I. Producing organism, fermentation, isolation and biological activity. 368 18


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