Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.4.21.4 (trypsin)
42,187 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Rat liver parenchymal cell binding, uptake, and proteolytic degradation of rat 125I-labeled high density lipoprotein (HDL) subfraction, HDL3 (1.10 less than d less than 1.210 g/ml), in which apo-A-I is the major polypeptide, were investigated. Structural and metabolic integrity of the isolated cells was verified by trypan blue exclusion, low lactic dehydrogenase leakage, expected morphology, and gluconeogenesis from lactate and pyruvate. 125I-labeled HDL3 was incubated with 10 X 10(6) cells at 37 degrees and 4 degrees in albumin and Krebs-Henseleit bicarbonate buffer, pH 7.4. Binding and uptake were determined by radioactivity in washed cells. Proteolytic degradation was determined by trichloroacetic acid-soluble radioactivity in the incubation medium. At 37 degrees, maximum HDL3 binding (Bmax) and uptake occurred at 30 min with a Bmax of 31 ng/mg dry weight of cells. The apparent dissociation constant of the HDL3 receptor system (Kd) was 60 X 10(-8) M, based on Mr = 28,000 of apo-A-I, the predominant rat HDL3 protein. Proteolytic degradation showed a 15-min lag and then constant proteolysis. After 2 hours 5.8% of incubated 125I-labeled HDL3 was degraded. Sixty per cent of cell radioactivity at 37 degrees was trypsin-releasable. At 37 degrees, 125I-labeled HDL3 was incubated with cells in the presence of varying concentrations of native (cold) HDL3, very low density lipoproteins, and low density lipoproteins. Incubation with native HDL3 resulted in greatest inhibition of 125I-labeled HDL3 binding, uptake, and proteolytic degradation. When 125I-labeled HDL3 was preincubated with increasing amounts of HDL3 antiserum, binding and uptake by cells were decreased to complete inhibition. Cell binding, uptake, and proteolytic degradation of 125I-labeled HDL3 were markedly diminished at 4 degrees. Less than 1 mM chloroquine enhanced 125I-labeled HDL3 proteolysis but at 5 mM or greater, chloroquine inhibited proteolysis with 125I-labeled HDL3 accumulation in cells. L-[U-14C]Lysine-labeled HDL3 was bound, taken up, and degraded by cells as effectively as 125I-labeled HDL3. These data suggest that liver cell binding, uptake, and proteolytic degradation of rat HDL3 are actively performed and linked in the sequence:binding, then uptake, and finally proteolytic degradation. Furthermore, there may be a specific HDL3 (lipoprotein A) receptor of recognition site(s) on the plasma membrane. Finally, our data further support our previous reports of the important role of liver lysosomes in proteolytic degradation of HDL3.
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PMID:Rat high density lipoprotein subfraction (HDL3) uptake and catabolism by isolated rat liver parenchymal cells. 18 84

A 45-year-old women had medullary tyroid carcinoma associated with Cushing's syndrome and galactorrhoea. Elevated plasma immunoreactive ACTH and cortisol were partially suppressed by intravenous dexamethasone, appreciably raised by lysine vasopressin, and urinary excretion of 17-oxogenic steroids slightly elevated by metyrapone. A large arterio-venous increase in plasma corticotrophin releasing factor-like activity across the thyroid gland was observed and tumour tissue contained corticotrophin releasing factor-like activity. Biologically active ACTH was not detected in tumour extracts before incubation with trypsin, but after trypsinization a value of 3.2 mU per gram was obtained. Arterial plasma contained biologically active ACTH (1.5 mU/100 ml) prior to trypsinization. Venous effluent from the thyroid gland contained biologically active (9.6 mU/100 ml) and immunoreactive ACTH (970 pg/ml) before trypsinization. Tumour extracts also contained prolactin production-stimulating activity. These findings can explain the Cushing's syndrome and the galactorrhoea both of which disappeared completely after thyroidectomy.
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PMID:Medullary thyroid carcinoma: ectopic production of peptides with ACTH-like, corticotrophin releasing factor-like and prolactin production-stimulating activities. 18 33

1. When ribonuclease T1 [EC 3.1.4.8] was treated with trypsin [EC 3.4.21.4] at pH 7.5 and 37 degrees, activity was lost fairly slowly. At higher temperatures, however, the rate of inactivation was markedly accelerated. The half life of the activity was about 2.5 h at 50 degrees and 1 h at 60 degrees. 3'-GMP and guanosine protected the enzyme significantly from tryptic inactivation. 2. Upon tryptic digestion at 50 degrees, the Lys-Tyr (41-42) and Arg-Val (77-78) bonds were cleaved fairly specifically, yielding two peptide fragments. One was a 36 residue peptide comprizing residues 42 to 77. The other was a 68 residue peptide composed of two peptide chains cross-linked by a disulfide bond between half-cystines -6 and -103, comprizing residues 1 to 41 and 78 to 104. 3. When the trinitrophenylated enzyme, in which the alpha-amino group of alanine-1 and the episolone-amino group of lysine 41 were selectively modified, was treated with trypsin at 37 degrees, the activity was lost fairly rapidly with a half life of about 4 h. In this case, tryptic hydrolysis occurred fairly selectively at the single Arg-Val bond. Thus the enzyme could be inactivated by cleavage of a single peptide bond in the molecule, an indication of the importance of the peptide region involving the single arginine residue at position 77 in the activity of ribonuclease T1.
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PMID:The structure and function of ribonuclease T1. XXII. Tryptic cleavages of the single lysyl and arginyl bonds in ribonuclease T1. 19 42

The exposure of apolipoproteins at the surface of human plasma high density lipoproteins (HDL) was assessed by their accessibility to agarose-immobilized forms of trypsin and chymotrypsin. Proteolysis of lipid-free apolipoproteins and the lipoprotein subfractions HDL2 (d = 1.08--1.125 g/ml) and HDL3 (d = 1.125--1.195 g/ml) that differ in lipid-to-protein ratio was compared by polyacrylamide gel electrophoresis and isoelectric focusing of the apolipoproteins and peptide fragments and by quantitation of the various carboxyl-terminal groups formed. Gel filtration of the proteolyzed lipoproteins on Sephadex G-150 column indicated that more than 90% of the apolipoproteins and peptides remain associated with lipoprotein complexes. Proteolysis of lipoproteins occurred more slowly and with less fragmentation of the lipoproteins and apolipoproteins than proteolysis of thelipid-free apolipoproteins or the proteolysis of lipoproteins by soluble proteases reported by other investigators. The difference in lipid content of HDL2 and HDL3 made little difference in their proteolysis. Proteolysis of the lipoproteins by agarose-trypsin was more rapid at 37 degrees C than at 22 degrees C, but the proteolytic products were similar and differed from the products from the lipid free proteins. Peptide fragments from lipoproteins were larger than those from lipid-free proteins, which suggests masking of potentially cleavable groups by lipid. The amounts (mol/g protein) of new carboxyl-terminal tyrosine and phenylalanine released by agarose -chymotrypsin were much greater from the lipid-free proteins, but about 3/4 of the tryptophan residues were inacessible in both lipoproteins and lipid-free proteins. In agarose-trypsin digestion, lysine residues were slightly more masked than arginine in the absence of lipids and much more so in the lipoproteins. However, in the lipoproteins apoA-II, which contains lysine but no arginine, was cleaved more rapidly and extensively by agarose-trypsin than apoA-I.
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PMID:Surface exposure of apolipoproteins in high density lipoproteins. I. Reactivities with agarose-immobilized proteases. 20 44

A previous report from this laboratory showed that binding of iodine-labeled human choriogonadotropin to Leydig tumor cells is not a reversible process (Ascoli, M., and Puett, D. (1978) J. Biol. Chem. 253, 4892--4899). Most of the cell-bound hormone was found to be degraded to 3'-monoiodotyrosine before being released from the cells, and the degradation process could be inhibited by the lysosomotropic agents NH4Cl, chloroquine, and Triton WR-1339. It is reported herein that the degradation of receptor-bound human choriogonadotropin is an energy-dependent process, which can be inhibited by compounds that interfere with glycolysis or oxidative phosphorylation (e.g. NaF, NaN3, NaCN, and 2-deoxyglucose). Hormone degradation is also inhibited by some protease inhibitors such as the chloromethyl ketones of lysine and phenylalanine, but not by specific trypsin inhibitors (e.g. p-aminobenzamidine and p-tosyl-L-arginine methyl ester). With the exception of NH4Cl, it was found that the compounds which inhibit hormone degradation also inhibit hormone-stimulated steroidogenesis. However, the present results involving dose dependency, and those given in the following paper (Ascoli, M. (1978) J. Biol. Chem. 253, 7839--7843), indicate that these two phenomena are not related.
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PMID:Inhibition of the degradation of receptor-bound human choriogonadotropin by lysosomotropic agents, protease inhibitors, and metabolic inhibitors. 21 38

When nucleosomal core histones were isolated from rat liver nuclei incubated with [14C]NAD+ and fractionated into the individual components (H2A, H2B, H3, and H4), [14C]adenosine diphosphate ribose (ADP-Rib) was found to be associated with all of them. However, while about 15% of the H2B molecules were modified, less than 2% of the other fractions contained radioactive ADP-Rib. The nucleotide attached to H2B was identified as a single monomer of ADP-Rib. On subjectint H2B to electrophoresis in polyacrylamide gels containing 2.5 M urea and 0.9 N acetic acid, one single band of H2B with 5% less mobility than the unomdified control was obtained. The linkage between H2B and ADP-Rib was rapidly hydrolyzed with 0.1 N NaOH or with 1 M neutral hydroxylamine. Hydrolysis of ADP-ribosylated H2B with trypsin generated a single peptide linked to ADP-Rib, which corresponded to the sequence Pro-Glu-Pro-Ala-Lys. We were able to dansylate the NH2-terminal proline, which proved that the imino group of this amino acid was not substituted. These findings, together with the chemical properties of the linkage, which were typical of those of an ester-like bond, strongly suggest that the ADP-Rib residue was linked to the gamma-COOH group of the glutamic acid in position 2 of H2B.
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PMID:ADP ribosylation of rat liver nucleosomal core histones. 21 26

Both the aminoacylation and isotopic ATP-PPi exchange activities of native and trypsin-modified methionyl-tRNA synthetases from Escherichia coli are specifically inactivated by incubation in the presence of periodate-treated initiator tRNA Met. The inactivation proceeds through the formation of a reversible Schiff's base between the epsilon-amino group of a lysine within the catalytic center of the enzyme and the 2',3'-aldehyde groups created at the 3'-terminal ribose of tRNA. The Schiff's base may be stabilized by reduction with sodium borohydride. Intact tRNA Met f competes with the inactivation by its dialdehyde. It has been verified in the case of the modified enzyme that the protection is afforded according to an equilibrium constant identical to that for tRNA Met f binding at the active site of the enzyme. Finally it is shown that the incorporation of one molecule of the dialdehyde of [14C]tRNA completely destroys the activity of the monomeric trypsin-modified methionyl-tRNA synthetase.
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PMID:Methionyl-tRNA synthetase from Escherichia coli. Inactivation and labeling by periodate-treated initiator tRNA. 22 89

Bisphosphoglycerate synthase (glycerate-1,3-P2 yields glycerate-2,3-P2) and phosphoglycerate mutase (glycerate-3-P formed from glycerate-2-P) are both phosphorylated by substrates at a histidine residue forming covalent intermediates which have been shown to function in the phosphoryl transfer reactions catalyzed by these enzymes (Rose, Z. B., and Dube, S. (1976) J. Biol. Chem. 251, 4817--4822). We have phosphorylated bisphosphoglycerate synthase from horse red blood cells with [U-32P]glycerate-2,3-P2, digested with trypsin, and purified the phosphopeptide. The amino acid sequence of the phosphohistidine peptide has been determined to be: His-Gly-Gln-Gly-Ala-Trp-Asn-Lys. In like manner, a phosphohistidyl peptide has now been purified from yeast phosphoglycerate mutase, for which the amino acid sequence is known (Winn, S. I., Watson, H. C., Fothergill, L. A., and Harkins, R. N. (1977) Biochem. Soc. Trans. 5, 657-659). The amino acid composition of the phosphopeptide indicates that histidine-8 was phosphorylated. The sequence of this peptide is closely homologous with the active site peptide from bisphosphoglycerate synthase. In yeast phosphoglycerate mutase, the denatured phosphoenzyme hydrolyzes with a single rate constant of 2.02 X 10(-4) s-1 at pH 3, 45 degrees C. The relevance of these observations to the enzymatic mechanism is discussed.
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PMID:Active site phosphohistidine peptides from red cell bisphosphoglycerate synthase and yeast phosphoglycerate mutase. 22 13

To distinguish ligand-induced structural states of the (Na+--K+)-ATPase, the purified membrane-bound enzyme isolated from rat kidneys was digested with trypsin in the presence of various combinations of Na+, K+, Mg++ and ATP. It was found that first the large and then the small polypeptide chain of the (Na+--K+)-ATPase was degraded, indicating that the lysine and arginine residues of the large chain are more exposed than are those of the small one. The (Na+--K+)-ATPase activity was inactivated in parallel with the degradation of the large polypeptide chain. After the degradation of the large polypeptide chain, about 75% of the (Na+--K+)-ATPase protein remained bound to the membrane, demonstrating that the split protein segments were only partially released. It was found that the combinations of ATP, Mg++, Na+ and K+ present during trypsin digestion influenced the time course and degree of degradation of the (Na+--K+)-ATPase protein. The degradations of the large and the small polypeptide chain were affected in parallel. Thus, certain ATP and ligand combinations influenced neither the degradation of the large nor the degradation of the small polypeptide chain, whereas by other combinations of ATP and ligands the degree of susceptibility of both polypeptide chains to trypsin was equally increased or reduced. In the absence of ATP the time course of trypsin digestion of the (Na+--K+)-ATPase was the same, whether Na+ or K+ was present. With low ATP concentrations (e.g., 0.1 mM), however, binding of Na+ or K+ led to different degradation patterns of the enzyme. If a high concentration of ATP (e.g. 10 mM) was present, Na+ and K+ also influenced the degradation pattern of the (Na+--K+)-ATPase, but differentially compared to that at low ATP concentrations, since the effects of Na+ and K+ were reversed. Furthermore, it was found that the degradation of the small chain was only influenced by certain combinations of ATP, Mg++, Na+ and K+ if the large chain was intact when the ligands were added to the enzyme. The described results demonstrate structural alterations of the (Na+--K+)-ATPase complex which are supposed to include a synchronous protrusion or retraction of both (Na+--K+)-ATPase subunits. The data further suggest that ATP and other ligands primarily alter the structure of the large (Na+--K+)-ATPase subunit. This structural alteration is presumed to lead to a synchronous movement of the small subunit of the enzyme. The structural state of the (Na+--K+)-ATPase is regulated by binding of Na+ or K+ to the enzyme-ATP complex. The effects of Na+ and K+ on the (Na+--K+)-ATPase structure are modulated by the ATP binding to "high affinity" and to "low affinity" ATP binding sites.
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PMID:Conformational changes of membrane-bound (Na+--K+)-ATPase as revealed by trypsin digestion. 22 7

The catalytic subunit of cyclic AMP-dependent protein kinase (from rabbit skeletal muscle; ATP:protein phosphotransferase, EC 2.7.1.37) was found to be irreversibly inactivated by chloromethyl ketone derivatives of lysine and phenylalanine, chemical reagents originally designed for labeling the active sites of the proteolytic enzymes trypsin and chymotrypsin. This inactivation was shown to occur at pH 7.5 and 22 degrees C, conditions under which chemically related alkylating reagents such as chloroacetamide and chloroacetic acid (which do not possess the amino acid side chain) fail to inactivate the enzyme. In the case of the chloromethyl ketone derivative of N alpha-tosyl-L-lysine, the enzyme could be protected by its nucleotide substrate (MgATP), by one of its protein substrates (histone H2b), and by its regulatory subunit which, upon binding, shields the active site of the catalytic subunit. Differential labeling experiments, together with kinetic studies of the rates of modification of the sulfhydryl groups in the enzyme before and after inactivation with the chloromethyl ketone, suggest that the loss of activity is associated with one (kinetically characterized) sulfhydryl group present either at the active site of the enzyme or at a site intimately associated with it. The general implications of these results regarding the interpretation of affinity labeling experiments carried out in complex mixtures of proteins or under in vivo conditions are discussed.
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PMID:Affinity labeling of the catalytic subunit of cyclic AMP-dependent protein kinase by N alpha-tosyl-L-lysine chloromethyl ketone. 22 53


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