Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0027960 (mole)
 21,279 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Some properties of homogeneous transketolase from pig liver were studied. It was shown that the pH optimum of the transketolase reaction lies within the range of 7.8--8.2. The isoelectric point is at pH 7.6--7.8. The molecular weight of transketolase is 138,000 +/- 3,000 as determined by the sedimentation equilibrium method and about 152,000 according to the data from gel filtration through Sephadex G-200. The enzyme molecule is a tetramer of the alpha 2 beta 2 type. The molecular weights of the alpha- and beta- subunits determined by polyacrylamide gel in the presence of sodium dodecyl sulfate are 52,000--56,000 and 27,000--29,000, respectively. Transketolase contains about two moles of TPP per mole of protein and does not require metal ions for its catalytic activity.
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PMID:[Properties of pig liver transketolase]. 46 97

The interaction of diethylpyrocarbonate (DEP) with the pyruvate dehydrogenase component (PDH) isolated from the pyruvate dehydrogenase complex (EC 1.2.4.1) results in a modification of 3-5 histidine residues per mole of enzyme, which simultaneously decreases the enzyme activity. After PDH inhibilion by DEP in the presence of dithiothreitol almost complete reactivation (94%) under the effect of neutral hydroxylamine is observed. In the absence of SH-groups protection incomplete reactivation by hydroxylamine (79%) is found. In the latter case titration with 5,5-dithio--bis-(2-nitrobenzoic acid) in 8 M urea showed that the DEP-modified protein contains less quantity of SH groups (by 4-8) as compared to the native enzyme. It is assumed that the DEP-modified SH-groups are not responsible for the enzyme activity. The differential spectrum of the modified and native PDH showed no changes within the range of 260-300 nm. TPP in combination with Mg2+ (10(-3) M) protectes PDH from being inactivated by DEP. TPP (10(-2) M) reactivates PDH by 70% after its complete inhibition by DEP. Similar protective action is manifested by ATP, ADP and inorganic pyrophosphate in the presence of Mg2+. A kinetic study showed a competitive type of PDH inhibition by DEP with respect to TPP. it is concluded that the histidine residues of PDH are involved in TPP binding.
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PMID:[Role of muscle pyruvate dehydrogenase histidine residues in thiamine pyrophosphate binding]. 98 22

Several metal complexes [(FeII(DPAH)2 (DPAH2 = 2,6-dicarboxyl pyridine), FeII(PA)2 (PAH = picolinic acid), FeII(bpy)2(2+), FeII(OPPh3)4(2+), (Cl8TPP)FeIIIX (X = Cl, OH, SCH2Ph) [Cl8TPP = tetrakis (2,6-dichlorophenyl)porphyrin], (TPP) FeIIICl (TPP = tetraphenylporphyrin), and CuI(tpy)2+ (typ = 2,2'-6,2"-terpyridine)] in combination with one of several reductants [DH2; PhNHNHPh (mimic of dihydroflavin), PhNHNH2, ascorbic acid (H2asc), and PhCH2SH (model ligand for cysteine residue)] catalytically activate O2 (1 atm) for the hydroxylation of saturated hydrocarbons (e.g. c-C6H12-->c-C6H11OH). This chemistry closely parallels that of cytochrome P-450 proteins, and both appear to involve a Fenton-like reactive intermediate), [LxFeOOH(DH)]. With cyclohexane as the substrate the dominant product is its ketone (as well as significant amounts of its hydroperoxide). 1,4-Cyclohexadiene (with two double-allylic carbon centers) undergoes dehydrogenation to give benzene, but also yields substantial amounts of phenol via ketonization of an allylic carbon. The 1:1 FeII(bpy)2(2+)/(PhNHNH2 or H2asc), FeII(PA)2/H2asc, and (Cl8TPP)FeIIICl/PhNHNH2 combinations initiate the autoxidation of 1,4-cyclohexadiene with turnover numbers (moles of product per mole of reductant) from 71 to 26, respectively (alpha-tocophenol reduces the turnover numbers by 20-80%). With respect to aerobic biology, the present results indicate that dysfunctional transition metals (degradation products of metalloproteins) in combination with biological reductants activate O2 for reaction with organic substrates. The level of activation is similar to that for Fenton reagents and cytochrome P-450 hydroxylases. Hence, dysfunctional transition metals, reductants, and O2 are a hazardous combination within a biological matrix.
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PMID:Iron(II)/reductant(DH2)-induced activation of dioxygen for the hydroxylation and ketonization of hydrocarbons; mimics for the cytochrome P-450 hydroxylase/reductase system. 778 1

A gut juice protein from Choristoneura fumiferana (spruce budworm) larvae that precipitates certain delta-endotoxins shows a unique specificity for the C-terminal amino acid sequence. Using homolog scanning mutants, we have identified a contiguous region of the Cry1Aa toxin which interacts with the 75-kDa toxin precipitating protein (TPP-75)' resulting in precipitation. The contiguous region from Cry1Aa can be transferred to Cry1Ac and results in an identical precipitation reaction. The precipitation reaction occurs rapidly and is unique in that the ratio of precipitating protein to toxin is low (estimated at 0.01), unlike antibody-antigen reactions which exhibit mole ratios close to 1. TPP-75 has been characterized as an elastase-like serine protease. We have taken advantage of this serine protease character and incorporated a radiolabel using an irreversible inhibitor. The radiolabel has allowed us to show the coincidence of the catalytically-inhibited TPP-75 with the toxin in a blotting assay and to follow the degradation of TPP-75 during storage. TPP-75 represents the first evidence that gut juice proteins may selectively attenuate the activity of delta-endotoxins, prior to binding to putative receptors on susceptible cells. TPP-75 should be evaluated as a possible resistance mechanism for those larvae that do not exhibit a receptor-based resistance.
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PMID:Spruce budworm elastase precipitates Bacillus thuringiensis delta-endotoxin by specifically recognizing the C-terminal region. 988 17

EmrE is an Escherichia coli multidrug transporter that confers resistance to a variety of toxins by removing them in exchange for hydrogen ions. The detergent-solubilized protein binds tetraphenylphosphonium (TPP(+)) with a K(D) of 10 nM. One mole of ligand is bound per approximately 3 mol of EmrE, suggesting that there is one binding site per trimer. The steep pH dependence of binding suggests that one or more residues, with an apparent pK of approximately 7.5, release protons prior to ligand binding. A conservative Asp replacement (E14D) at position 14 of the only membrane-embedded charged residue shows little transport activity, but binds TPP(+) at levels similar to those of the wild-type protein. The apparent pK of the Asp shifts to <5.0. The data are consistent with a mechanism requiring Glu14 for both substrate and proton recognition. We propose a model in which two of the three Glu14s in the postulated trimeric EmrE homooligomer deprotonate upon ligand binding. The ligand is released on the other face of the membrane after binding of protons to Glu14.
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PMID:A membrane-embedded glutamate is required for ligand binding to the multidrug transporter EmrE. 1063 27