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:3.4.21.1 (chymotrypsin)
10,938 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Quiescent, contact inhibited H-35 rat hepatoma cell cultures maintained in minimal essential medium contain a very low level of ornithine decarboxylase activity. However, 2 h after the addition of 10% fetal calf serum to the culture medium, the enzyme activity increases by approx. 100-fold. This increase can be completely inhibited by the simultaneous addition of 10(-2) M putrescine. The presence of putrescine elicits the appearance of an intracellular inhibitor of ornithine decarboxylase. This inhibitor of ornithine decarboxylase has a molecular weight of 26500, is sensitive to the action of chymotrypsin and is noncompetitive with respect to ornithine. The intracellular appearance of this inhibitor is sensitive to cycloheximide but is only partially inhibited by actinomycin D.
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PMID:The appearance of an ornithine decarboxylase inhibitory protein upon the addition of putrescine to cell cultures. 17 75

The large subunit of Escherichia coli carbamoyl phosphate synthetase (a polypeptide of 117.7 kDa that consists of two homologous halves) is responsible for carbamoyl phosphate synthesis from NH3 and for the binding of the allosteric activators ornithine and IMP and of the inhibitor UMP. Elastase, trypsin, and chymotrypsin inactivate the enzyme and cleave the large subunit at a site approximately 15 kDa from the COOH terminus (demonstrated by NH2-terminal sequencing). UMP, IMP, and ornithine prevent this cleavage and the inactivation. Upon irradiation with ultraviolet light in the presence of [14C]UMP, the large subunit is labeled selectively and specifically. The labeling is inhibited by ornithine and IMP. Cleavage of the 15-kDa COOH-terminal region by prior treatment of the enzyme with trypsin prevents the labeling on subsequent irradiation with [14C]UMP. The [14C]UMP-labeled large subunit is resistant to proteolytic cleavage, but if it is treated with SDS the resistance is lost, indicating that UMP is cross-linked to its binding site and that the protection is due to conformational factors. In the presence of SDS, the labeled large subunit is cleaved by trypsin or by V8 staphylococcal protease at a site located 15 or 25 kDa, respectively, from the COOH terminus (shown by NH2-terminal sequencing), and only the 15- or 25-kDa fragments are labeled. Similarly, upon cleavage of the aspartyl-prolyl bonds of the [14C]UMP-labeled enzyme with 70% formic acid, labeling was found only in the 18.5-kDa fragment that contains the COOH terminus of the subunit. Thus, UMP binds to the COOH-terminal domain.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Domain structure of the large subunit of Escherichia coli carbamoyl phosphate synthetase. Location of the binding site for the allosteric inhibitor UMP in the COOH-terminal domain. 198 78

The production of urea and ornithine is increased greatly in spleen cell cultures of an allograft recipient in the presence of donor cells (secondary MLC) in comparison to that of primary MLC (without previous allograft). This phenomenon appears after 24 hr of culture and reaches its maximum at 48 hr. The greatest increase in urea production is observed when the recipient spleen cells are collected at the time of allograft rejection. To obtain this extra production of urea, the stimulating cells in MLC should specifically be of the donor type or at least bear one homology with donor cells at the K or D locus. The increased production of urea and ornithine during MLC results from the action of a lymphokine released by recipient cells in the presence of donor cells. This factor acts upon cells present in bone marrow, spleen, and elicited peritoneal cells but is absent or is present in smaller quantities in thymus and lymph node cells. Target cells of this factor possess numerous macrophage features and could be immature cells of the macrophage line. The lymphokine responsible for this phenomenon is heat-stable, destroyed by trypsin, chymotrypsin, and neuraminidase, and has a m.w. around 32,000. It acts upon its target cells by increasing arginase activity, which results in the production of a large amount of ornithine, an important precursor of polyamine biosynthesis.
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PMID:Evidence for a lymphokine enhancing arginase activity during allograft rejection. 618 26

A peptide mixture containing 21 peptide sequences has been constructed to test the Bowman-Birk inhibitor reactive-site loop motif as the basis of inhibition for a range of serine proteases. The 21 peptides are all based on an 11 amino acid sequence designed from a Bowman-Birk like inhibitor reactive-site loop. Variation has been introduced at the P1 site of the loop, which has been randomised to include all the natural L-amino acids (except for cysteine), plus the non-natural L-amino acids ornithine and norleucine, The mixture of peptides was screened for specific binding to immobilised porcine pancreatic elastase, subtilisin BPN', alpha-chymotrypsin, trypsin, anhydro-alpha-chymotrypsin and anhydrotrypsin. Five peptides from the mixture bind to alpha-chymotrypsin, two of which also bind to anhydro-alpha-chymotrypsin, and two peptides bind trypsin, neither of which binds to anhydro-trypsin. The competitive inhibition constants (K(i)) and the rates of proteolytic hydrolysis of the individual peptides with their respective enzymes were determined. The rates of hydrolysis were found to vary widely and show little correlation with the K(i) values. In the case of the alpha-chymotrypsin inhibitors, the peptides with the lowest K(i) (0.1-0.05 mM) were the only peptides that bound to anhydro-alpha-chymotrypsin. However, no peptides bound to anhydrotrypsin, suggesting a fundamental difference in the way that alpha-chymotrypsin and trypsin are inhibited by these cyclic peptides.
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PMID:Synthesis of a mixture of cyclic peptides based on the Bowman-Birk reactive site loop to screen for serine protease inhibitors. 755 1

Trypanosoma brucei ornithine decarboxylase was reconstituted by coexpression of two polypeptides corresponding to residues 1-305 and residues 306-425 in Escherichia coli. The two peptides were coexpressed, at wild-type levels, from a single transcriptional unit that was separated by a 15-nucleotide untranslated region containing a ribosome binding site. The fragmented enzyme was purified and analyzed. The N- and C-terminal peptides are tightly associated into a fully active tetramer which has the same molecular weight as the native dimer. The kinetic constants (Km and kcat) measured for the decarboxylation of ornithine are identical to those obtained for the wild-type enzyme. These results suggest that the enzyme is organized into two structural domains, with a domain boundary in the region of amino acid 305. In contrast, the individual N- and C-terminal peptides are expressed primarily as inclusion bodies. Small quantities of soluble N-terminal peptide could be purified. This truncated protein is capable of inhibiting the wild-type enzyme, suggesting that it is folded into a native-like structure. Limited proteolysis with trypsin or chymotrypsin identifies a likely surface loop at amino acids 160-170, present in both the mouse and T. brucei enzyme, which positions one or more functionally important active site residues (e.g., Lys169). Kinetic analysis of a chimeric enzyme composed of T. brucei and mouse ornithine decarboxylase suggests that the substrate carboxylate binding determinant is located between residues 1 and 170.
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PMID:Domain organization and a protease-sensitive loop in eukaryotic ornithine decarboxylase. 757 30

The structural and functional domains of Escherichia coli carbamoyl phosphate synthetase (CPS) have been identified by limited proteolysis. Incubation of CPS with several proteases, including trypsin, chymotrypsin, subtilisin and endoproteinase Asp-N, under native conditions, causes a time-dependent loss of enzymatic activity and the generation of a common fragmentation pattern. Amino-terminal sequencing studies demonstrated that the initial cleavage event by trypsin occurred at the carboxy-terminal end of the large subunit. The ultimate fragments produced in most of the proteolysis studies, 35- and 45-kDa peptides, were derived from areas corresponding to the putative ATP binding regions. Substrate protection studies showed that the addition of ligands did not affect the final fragmentation pattern of the protein. However, ornithine and UMP were found to significantly reduce the rate of inactivation by inhibition of proteolytic cleavage. MgATP and IMP provided modest protection whereas bicarbonate and glutamine showed no overall effect on proteolysis. Limited proteolysis by endoproteinase Asp-N resulted in the production of a fragment (or multiple fragments) which contained enzymatic activity but had lost all regulation by the allosteric ligands, UMP and ornithine. The small subunit has been shown to be protected from proteolysis by the large subunit. Proteolysis of the isolated small subunit resulted in the generation of a stable 31-kDa species which contained 10% of the original glutaminase activity. These studies demonstrate that a portion of the C-terminal end of the large subunit can be excised without entirely destroying the ability of CPS to catalyze the formation of carbamoyl phosphate.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Mapping the structural domains of E. coli carbamoyl phosphate synthetase using limited proteolysis. 764 1

A novel 9 kD protein inhibitor of trypsin and related proteinases was purified from culture filtrate of Yersinia pseudotuberculosis by ultrafiltration, affinity chromatography, and gel filtration. The protein is stable at pH from 1 to 9. The inhibitor activity dramatically decreases at temperature above 37 degrees C. The purified inhibitor significantly suppresses activities of an endogenous trypsin-related proteinase and trypsin but does not affect chymotrypsin, pepsin, and papain. One molecule of yersinia inhibitor binds two molecules of endogenous trypsin-related proteinase and about one trypsin molecule. The Ki for yersinia proteinase is 1.7.10(-7) and Ki for trypsin is 2.4.10(-7). Amino acid composition of the inhibitor is characterized by the presence of beta-aminobutyric acid and ornithine and relatively high contents of alanine and arginine whereas cysteine, histidine, and proline are absent.
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PMID:[Trypsin and microbial serine proteinase inhibitors isolated from Yersinia pseudotuberculosis]. 901 Dec 35

We previously demonstrated that the feeding of guanidinated casein, whose lysine residues are converted to homoarginine, stimulates pancreatic secretion much higher than that of intact casein in chronic bile-pancreatic juice (BPJ)-diverted rats, which suggests that the guanidino group is involved in BPJ-independent enhancement of pancreatic secretion. However, the role of the guanidino group in the protein for the enhancement of pancreatic secretion has not been clarified. In this study, we examined the stimulation of pancreatic secretion by a arginine rich dietary protein, protamine (25, 50 mg/ml), and then determined whether the guanidino group in protamine was responsible for the secretory responses in normal and BPJ-diverted rat by comparison with pancreatic secretion between intact and deguanidinated protamine. The deguanidinated protamine was prepared by converting arginine residues of salmon protamine to ornithine using heated hydrazine (conversion rate of arginine residue was 87%). In normal rats, pancreatic protein and chymotrypsin secretion were stimulated in dose-response fashion after a duodenal instillation of native protamine solution (25, 50 mg in 1 ml). In chronic BPJ-diverted rats, native protamine (25 mg) maximally stimulated pancreatic protein and protease secretion. In contrast, deguanidinated protamine (50 mg in 1 ml) did not stimulate pancreatic secretion in both normal and BPJ-diverted rats. In addition, the duodenal administration of arginine, which is equal to the amount contained in 50 mg of native protamine, had no effect on pancreatic secretion in both rats. These results suggest that a naturally occurring protein, protamine, stimulates pancreatic secretion by a luminal BPJ-independent mechanism and that the guanidino group in this protein is responsible for stimulating pancreatic secretion in BPJ-diverted rats.
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PMID:Guanidino group is involved in the stimulation of exocrine pancreatic secretion by protamine in normal and chronic bile-pancreatic juice-diverted rats. 1009 Apr 14

N5-(L-1-carboxyethyl)-L-ornithine synthase [E.C. 1.5.1.24] (CEOS) from Lactococcus lactis has been cloned, expressed, and purified from Escherichia coli in quantities sufficient for characterization by biophysical methods. The NADPH-dependent enzyme is a homotetramer (Mr approximately equal to 140,000) and in the native state is stabilized by noncovalent interactions between the monomers. The far-ultraviolet circular dichroism spectrum shows that the folding pattern of the enzyme is typical of the alpha,beta family of proteins. CEOS contains one tryptophan (Trp) and 19 tyrosines (Tyr) per monomer, and the fluorescence spectrum of the protein shows emission from both Trp and Tyr residues. Relative to N-acetyltyrosinamide, the Tyr quantum yield of the native enzyme is about 0.5. All 19 Tyr residues are titratable and, of these, two exhibit the uncommonly low pKa of approximately 8.5, 11 have pKa approximately 10.75, and the remaining six titrate with pKa approximately 11.3. The two residues with pKa approximately 8.5 contribute approximately 40% of the total tyrosine emission, implying a relative quantum yield >1, probably indicating Tyr-Tyr energy transfer. In the presence of NADPH, Tyr fluorescence is reduced by 40%, and Trp fluorescence is quenched completely. The latter result suggests that the single Trp residue is either at the active site, or in proximity to the sequence GSGNVA, that constitutes the beta alphabeta fold of the nucleotide-binding domain. Chymotrypsin specifically cleaves native CEOS after Phe255. Although inactivated by this single-site cleavage of the subunit, the enzyme retains the capacity to bind NADPH and tetramer stability is maintained. Possible roles in catalysis for the chymotrypsin sensitive loop and for the low pKa Tyr residues are discussed.
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PMID:N5-(L-1-carboxyethyl)-L-ornithine synthase: physical and spectral characterization of the enzyme and its unusual low pKa fluorescent tyrosine residues. 1054 58

Electrical field stimulation (EFS)-induced non-adrenergic non-cholinergic (NANC) relaxation responses in the rabbit vaginal wall were investigated. These NANC responses were partially inhibited with the nitric oxide synthase (NOS) inhibitors N(G)-nitro-L-arginine methyl ester (L-NAME; 500 microM), N(G)-nitro-L-arginine (300 microM) or N-iminoethyl-L-ornithine (500 microM) or the selective soluble guanylate cyclase inhibitor 1H-[1,2,4]oxadiazolo[4,3,-a]quinoxalin-1-one (ODQ, 10 microM). Application of L-NAME and ODQ concomitantly did not increase the degree of inhibition. L-NAME or ODQ were observed to be more effective at low frequencies. The resistant part of the responses was more pronounced at higher frequencies and was completely inhibited by tetrodotoxin (1 microM). Exogenous application of the peptides vasoactive intestinal peptide (VIP), pituitary adenylate cyclase activating peptide (PACAP-27 and PACAP-38), peptide histidine methionine (PHM), peptide histidine valine (PHV), helospectin-I or -II induced a relaxation response. Calcitonin gene-related peptide or substance P did not cause any relaxation. The peptidase alpha-chymotrypsin (type II; 2 units ml(-1)) did not affect non-nitrergic NANC responses, although it did inhibit relaxation responses elicited by exogenous VIP, PACAP-27, PACAP-38, PHM, PHV, helospectin-I or -II. K(+) channel inhibitors apamin (1 microM) or charybdotoxin (100 nM) when used alone or in conjunction did not affect non-nitrergic NANC responses. The non-nitrergic NANC responses were not associated with any increase in intracellular cyclic adenosine-3', 5'-monophosphate (cyclic AMP) or cyclic guanosine-3', 5'-monophosphate (cyclic GMP) concentrations. The peptide-induced relaxations were all associated with increases in cyclic AMP concentrations. These results suggest that a neuronal factor elicits non-nitrergic NANC responses in the rabbit vaginal wall. The identity of this factor remains to be established.
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PMID:Characterization of the non-nitrergic NANC relaxation responses in the rabbit vaginal wall. 1181 90


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