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)

This work was done to discover how those nonphotosynthetic tissues of the Araceae that become thermogenic release, as CO2, carbon recently fixed by phosphoenolpyruvate carboxylase. Extracts of clubs of the spadix of Arum maculatum showed no activity for phosphoenolpyruvate carboxykinase and low activities of NADP malic enzyme. NAD malic enzyme activity in the above extracts and in those of thermogenic tissues of other Araceae was appreciable. Analysis of homogenates of clubs of Typhonium giraldii by differential centrifugation and sucrose gradients showed that NAD malic enzyme was confined to mitochondria. Centrifugation of mitochondria after freezing and thawing left all the NAD malic enzyme in the supernatant. NAD malic enzyme in isolated, intact mitochondria was completely latent, and was completely protected from exogenous trypsin. The responses of this latency and protection to different concentrations of Triton X-100 suggested that none of the NAD malic enzyme was accessible from either the outside or the intermembrane space of the mitochondria. Treatment of excised clubs of A. maculatum with 2-N-butylmalonate largely prevented the development of the rapid respiration responsible for thermogenesis, and severely inhibited dark fixation of 14CO2. The conclusion is that in mature clubs of the Araceae phosphoenolpyruvate is converted to malate in the cytosol by phosphoenolpyruvate carboxylase and NAD malate dehydrogenase, and that this malate then enters the mitochondrial matrix where it is converted to pyruvate by NAD malic enzyme.
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PMID:Role and location of NAD malic enzyme in thermogenic tissues of Araceae. 642 Dec 32

1. Staphylococcal enterotoxin A (SEA) was exposed in a state of limited proteolysis to five kinds of proteolytic enzymes: papain, pepsin, pronase, trypsin and alpha-chymotrypsin. SEA was found to be sensitive to the action of three of them: papain, pepsin and pronase. 2. Four fragments were produced after papain proteolysis of SEA in the presence of beta-mercaptoethanol. 3. Papain processing of SEA does not influence its capacity to interact with antibodies to intact toxin, but the capacity of SEA to hydrolyse NAD to nicotinamide (NA) and adenosinediphosphatribose (ADP-ribose) completely disappears. 4. SEA under the action of pepsin and pronase has been hydrolysed to small peptides, which appear to be moving with the front of leading dye in disc-electrophoresis.
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PMID:Properties of staphylococcal enterotoxin A under limited proteolysis. 704 84

Incubation of crude normal rat kidney membranes with activated cholera toxin in the presence of DTP, ATP and NAD results in a 10--20 fold stimulation of adenylate cyclase activity. Optimal choleragen activation f the cyclase is shown to be dependent upon the presence of a plasma membrane-associated reconstituting activity, which can be dissociated from the membranes by washing with 10 mM potassium phosphate buffer, pH 7.5, containing 5 mM EDTA and 0.1 mM dithiothreitol. choleragen-catalyzed ADP ribosylation of plasma membrane substrate proteins also requires the presence of reconstituting activity factor. Sephadex G-150 filtration of solubilized reconstituting activity shows a peak activity eluting in the region corresponding to a protein with a molecular weight of approx. 13,000. Reconstituting activity is eluted from DEAE-cellulose at a salt concentration of 40--100 mM KCl. This active factor is not destroyed by trypsin treatment or by boiling for 30 min. These observations indicate that an endogenous membrane-associated factor, along with GTP, may be involved in modulating the ability of choleragen to activate adenylate cyclase.
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PMID:Plasma membrane-associated component(s) that confer(s) cholera toxin sensitivity to adenylate cyclase. 705 18

1. Sequence analysis of the NADPH domain (residues 158--293) and of the interface domain (365--478) was based on 12 CNBr fragments, which were isolated using ion-exchange chromatography and paper methods. Fragments with more than 15 residues were digested further with trypsin and chymotrypsin. The isolated peptides were sequenced by automated solid-phase Edman degradation. All sequenced peptides were ordered and overlapped by computerized comparisons with a complete sequence guessed from the electron density map of the protein. In the case of short CNBr fragments, this alignment was confirmed by the sequence analysis of protein fragments resulting from incomplete CNBr cleavage. 2. In the NADPH domain, residue 197, which is involved in an induced-fit mechanism, was identified as a tyrosine. The structure of the NADPH domain is probably homologous with the NAD domain of lipoamide dehydrogenase and with the FAD domain of several proteins, but not with NADPH domains of known chain-fold in other proteins. 3. The paper completes the sequence analysis of glutathione reductase so that the enzyme is now known in atomic detail. The numbering scheme of the chemically determined sequence will be used henceforth in crystallographic studies also. As inferred from the sequence data each of the two identical chains contains 478 amino acid residues, the composition being Cys10, Asp21, Asn17, Thr31, Ser31, Glu29, Gln11, Pro24, Gly43, Ala42, Val44, Met15, Ile29, Leu34, Tyr13, Phe14, Lys34, His16. Arg17, and Trp3. From these data an Mr of 2 x 51 600 was calculated for the FAD-free apoenzyme and an Mr of 2 x 42 400 for the holoenzyme.
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PMID:Glutathione reductase from human erythrocytes. The sequences of the NADPH domain and of the interface domain. 706 May 51

The mitochondrial nicotinamide nucleotide transhydrogenase enzyme (EC 1.6.1.1) is inhibited by treatment with dicyclohexylcarbodiimide or diethylpyrocarbonate. Both inhibitions are pseudo first order with respect to incubation time, and both reaction orders with respect to inhibitor concentration are close to unit, indicating that in each case inhibition results from the binding of one inhibitor molecule per active unit of the transhydrogenase enzyme. In the presence of either inhibitor, both the energy-linked and the nonenergy-linked transhydrogenation reactions are inhibited at about the same rate. The water-soluble carbodiimide, N-ethyl-N'-(3-dimethylaminopropyl) carbodiimide, showed no inhibition, however, NAD(H) and reduced or oxidized 3-acetylpyridine adenine dinucleotide protected the enzyme against inhibition by dicyclohexylcarbodiimide, while NADP (but not NADPH) appeared to increase the rate of inhibition. Substrates did not protect the enzyme against inhibition by diethylpyrocarbonate. [14C]dicyclohexylcarbodiimide labeled the transhydrogenase enzyme in submitochondrial particles. Treatment of labeled particles with trypsin resulted in fragmentation of the transhydrogenase enzyme and loss of a labeled polypeptide of Mr = approximately 100,000 as determined by polyacrylamide gel electrophoresis.
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PMID:Inhibition of the mitochondrial nicotinamide nucleotide transhydrogenase by dicyclohexylcarbodiimide and diethylpyrocarbonate. 726 46

Bovine heart submitochondrial particle transhydrogenase is inhibited by cations in a concentration and pH-dependent manner, and non-energy-linked transhydrogenation is inhibited to a greater extent by metals than the energy-linked reaction. The inhibition of the enzyme by Mg2+ is competitive with the NADP substrate and non-competitive with the NAD substrate. Mg2+ stimulates inactivation of the enzyme by 5,5'-dithiobis(2-nitrobenzoic acid), and protects against thermal and proteolytic inactivation. This suggests that Mg2+ binding in the NADP site alters transhydrogenase to a more thermostable conformation, which is less susceptible to attack by trypsin and more reactive with 5,5'-dithiobis(2-nitrobenzoic acid). Other cation inhibitors mimic Mg2+ in these properties. The order of effectiveness of the inhibitors tested is La3+ greater than Mn2+ greater than Ca2+ congruent to Mg2+ greater than Sr2+ greater than Na+ congruent to K+. This order is described by the Irving-Williams order for the stability of metal-ligand complexes, suggesting that carboxylates or amines may comprise the inhibitory cation binding site.
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PMID:The effect of metal ions on mitochondrial pyridine dinucleotide transhydrogenase. 735 84

Submitochondrial particles catalyze transhydrogenation from NADPH to [14C]NADP. This transhydrogenation is energy-linked, since its rate increases several-fold when the system is energized by succinate oxidation in the presence of rotenone (inhibitable by antimycin A or uncouplers), or by ATP hydrolysis (inhibitable by rutamycin or uncouplers). As in the case of transhydrogenation reactions from NAD(P)H to 3-ace-tylpyridine adenine dinucleotide phosphate and to thionicotinamide adenine dinucleotide phosphate, transhydrogenation from NADPH to [14C]NADP is also sensitive to treatment of the particles with trypsin or the arginyl residue modifier, butanedione. However, unlike the former reactions, transhydrogenation from NADPH to [14C]NADP cannot accumulate energy in the concentrations of the products, because, except for radioactivity, the nature and concentrations of the reactants and products remain unchanged throughout the course of the reaction. Therefore, the unrecoverable energy utilization by this region could be ascribed to an entropic component of the process, very likely an enzyme conformation change necessary for facilitation of hydride ion transfer from NADPH to [14C]NADP. This interpretation is in agreement with our previous kinetic evidence for enzyme conformation change associated with energy-linked transhydrogenation from NADH to 3-acetylpyridine adenine dinucleotide phosphate and thionicotinamide adenine dinucleotide phosphate, and with our conclusions regarding the mechanism of action of the transhydrogenase enzyme (Galante, Y.M., Lee, Y., and Hatefi, Y. (1980) J. Biol. Chem. 255, 9641-9646).
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PMID:Energy-linked transhydrogenation from NADPH to [14C]NADP. 743 83

The mitochondrial energy-linked transhydrogenase enzyme catalyzes hydride ion transfer between NAD and HADP, of which the reaction NADH leads to NADP is slow in the absence of energy and is accelerated 10-fold or more when the mitochondrial membrane is energized by ATP hydrolysis or respiration. The enzyme is a proton pump and effects proton translocation coupled to hydride ion transfer from NADPH to NAD (Earle, S.R., and Fisher, R.R. (1980) J. Biol Chem. 255, 827-830). The present studies have shown that submitochondrial particles also catalyze transhydrogenation from NADPH to two NADP analogs, namely 3-acetylpyridine adenine dinucleotide phosphate (AcPyADP) and thionicotinamide adenine dinucleotide phosphate (thioNADP). Both reaction rates are greatly accelerated when the system is energized by ATP hydrolysis (inhibitable by uncouplers or rutamycin) or succinate oxidation (inhibitable by uncouplers or antimycin A). As in the case of NAD(H) in equilibrium with NADP(H) reactions, the transhydrogenations from NADPH to AcPyADP and thioNADP are inhibited by treatment of submitochondrial particles with trypsin or the arginyl residue modifier, butanedione. The Km values of the above substrates and the Vmax values under energy-linked conditions have been determined. The finding that the mitochondrial energy-linked transhydrogenase enzyme catalyzes transhydrogenation from NADPH to NADP analogs has revealed features regarding substrate site specificities and the effect of substrates on the directionality of proton translocation by the enzyme.
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PMID:Energy-linked mitochondrial transhydrogenation from NADPH to NADP analogs. 743 92

NAD(P)H:quinone acceptor oxidoreductase (EC 1.6.99.2) (DT-diaphorase) is a FAD-containing reductase that catalyzes a unique 2-electron reduction of quinones. It consists of 2 identical subunits. In this study, it was found that the carboxyl-terminal portion of the 2 subunits can be cleaved by various proteases, whereas the amino-terminal portion cannot. It was also found that proteolytic digestion of the enzyme can be blocked by the prosthetic group FAD, substrates NAD(P)H and menadione, and inhibitors dicoumarol and phenindione. Interestingly, chrysin and Cibacron blue, 2 additional inhibitors, cannot protect the enzyme from proteolytic digestion. The results obtained from this study indicate that the subunit of the quinone reductase has a 2-domain structure, i.e., an amino-terminal compact domain and a carboxyl-terminal flexible domain. A structural model of the quinone reductase is generated based on results obtained from amino-terminal and carboxyl-terminal protein sequence analyses and electrospray mass spectral analyses of hydrolytic products of the enzyme generated by trypsin, chymotrypsin, and Staphylococcus aureus protease. Furthermore, based on the data, it is suggested that the binding of substrates involves an interaction between 2 structural domains.
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PMID:A two-domain structure for the two subunits of NAD(P)H:quinone acceptor oxidoreductase. 751 54

Transhydrogenase catalyses the reversible transfer of reducing equivalents between NAD(H) and NADP(H) to the translocation of protons across a membrane. Uniquely in Rhodospirillum rubrum, the NAD(H)-binding subunit (called Ths) exists as a separate subunit which can be reversibly dissociated from the membrane-located subunits. We have expressed the gene for R. rubrum Ths in Escherichia coli to yield large quantities of protein. Low concentrations of either trypsin or endoproteinase Lys-C lead to cleavage of purified Ths specifically at Lys227-Thr228 and Lys237-Glu238. Observations on the one-dimensional 1H-NMR spectra of Ths before and after proteolysis indicate that the segment which straddles the cleavage sites forms a mobile loop protruding from the surface of the protein. Alanine dehydrogenase, which is very similar in sequence to the NAD(H)-binding subunit of transhydrogenase, lacks this segment. Limited proteolytic cleavage has little effect on some of the structural characteristics of Ths (its dimeric nature, its ability to bind to the membrane-located subunits of transhydrogenase, and the short-wavelength fluorescence emission of a unique Trp residue) but does decrease the NADH-binding affinity, and does lower the catalytic activity of the reconstituted complex. The presence of NADH protects against trypsin or Lys-C cleavage, and leads to broadening, and in some cases, shifting, of NMR spectral signals associated with amino acid residues in the surface loop. This indicates that the loop becomes less mobile after nucleotide binding. Observation by NMR during a titration of Ths with NAD+ provides evidence of a two-step nucleotide binding reaction. By introducing an appropriate stop codon into the gene coding for the polypeptide of E. coli transhydrogenase cloned into an expression vector, we have prepared the NAD(H)-binding domain equivalent to Ths. The E. coli protein is sensitive to proteolysis by either trypsin or Lys-C in the mobile loop. Judging by the effect of NADH on its NMR spectrum and on the fluorescence of its Trp residues, the protein is capable of binding the nucleotide though it is unable to dock with the membrane-located subunits of transhydrogenase from R. rubrum.
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PMID:Conformational dynamics of a mobile loop in the NAD(H)-binding subunit of proton-translocating transhydrogenases from Rhodospirillum rubrum and Escherichia coli. 755 67


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