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Peutz-Jeghers polyps, dysplasia, and K-ras codon 12 mutations.
Entius MM, Westerman AM, Giardiello FM, van Velthuysen ML, Polak MM, Slebos RJ, Wilson JH, Hamilton SR, Offerhaus GJ
(1997) Gut 41: 320-2
MeSH Terms: Autoradiography, Codon, Genes, ras, Glycine, Humans, Peutz-Jeghers Syndrome, Point Mutation, Polymerase Chain Reaction, Valine
Show Abstract · Added March 5, 2014
BACKGROUND - Peutz-Jeghers syndrome (PJS) is a rare, autosomal dominant, polyposis syndrome, associated with an increased risk of gastrointestinal and extragastrointestinal malignancy. Occasionally dysplasia occurs in PJS polyps.
AIMS - In colorectal carcinomas, mutations in codon 12 of the K-ras oncogene are common and are found at similar frequency in precursor adenomas. Therefore, K-ras codon 12 point mutations in PJS polyps, were evaluated.
MATERIALS AND METHODS - Fifty two PJS polyps, including four with dysplasia, collected from 19 patients with PJS, were analysed for mutations in the K-ras codon 12 by a mutant enriched polymerase chain reaction procedure, followed by allele specific oligodeoxynucleotide hybridisation.
RESULTS - A K-ras codon 12 mutation was identified, in one colonic polyp with dysplasia. The mutation was found in the non-neoplasmic epithelial cells and not in the dysplastic component of the polyp.
CONCLUSIONS - K-ras codon 12 point mutations are very rare in PJS polyps, by contrast with colorectal adenomas. The findings support previous evidence that there seems to be no intrinsic relation between K-ras codon 12 mutation and dysplasia.
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9 MeSH Terms
An active site substitution, F87V, converts cytochrome P450 BM-3 into a regio- and stereoselective (14S,15R)-arachidonic acid epoxygenase.
Graham-Lorence S, Truan G, Peterson JA, Falck JR, Wei S, Helvig C, Capdevila JH
(1997) J Biol Chem 272: 1127-35
MeSH Terms: Animals, Bacterial Proteins, Binding Sites, Cytochrome P-450 Enzyme System, Gas Chromatography-Mass Spectrometry, Mixed Function Oxygenases, Models, Molecular, Mutagenesis, Site-Directed, NADP, NADPH-Ferrihemoprotein Reductase, Oxygenases, Phenylalanine, Stereoisomerism, Valine
Show Abstract · Added November 7, 2018
Cytochrome P450 BM-3 catalyzes the high turnover regio- and stereoselective metabolism of arachidonic and eicosapentaenoic acids. To map structural determinants of productive active site fatty acid binding, we mutated two amino acid residues, arginine 47 and phenylalanine 87, which flank the surface and heme ends of the enzyme's substrate access channel, respectively. Replacement of arginine 47 with glutamic acid resulted in a catalytically inactive mutant. Replacement of arginine 47 with alanine yielded a protein with reduced substrate binding affinity and arachidonate sp3 carbon hydroxylation activity (72% of control wild type). On the other hand, arachidonic and eicosapentaenoic acid epoxidation was significantly enhanced (154 and 137%, of control wild type, respectively). As with wild type, the alanine 47 mutant generated (18R)-hydroxyeicosatetraenoic, (14S,15R)-epoxyeicosatrienoic, and (17S,18R)-epoxyeicosatetraenoic acids nearly enantiomerically pure. Replacement of phenylalanine 87 with valine converted cytochrome P450 BM-3 into a regio- and stereoselective arachidonic acid epoxygenase ((14S,15R)-epoxyeicosatrienoic acid, 99% of total products). Conversely, metabolism of eicosapentaenoic acid by the valine 87 mutant yielded a mixture of (14S,15R)- and (17S,18R)-epoxyeicosatetraenoic acids (26 and 69% of total, 94 and 96% optical purity, respectively). Finally, replacement of phenylalanine 87 with tyrosine yielded an inactive protein. We propose that: (a) fatty acid oxidation by P450 BM-3 is incompatible with the presence of residues with negatively charged side chains at the surface opening of the substrate access channel or a polar aromatic side chain in the vicinity of the heme iron; (b) the high turnover regio- and stereoselective metabolism of arachidonic and eicosapentaenoic acids involves charge-dependent anchoring of the fatty acids at the mouth of the access channel by arginine 47, as well as steric gating of the heme-bound oxidant by phenylalanine 87; and (c) substrate binding coordinates, as opposed to oxygen chemistries, are the determining factors responsible for reaction rates, product chemistry, and, thus, catalytic outcome.
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MeSH Terms
The effect of diazepam on neonatal seizure: in vivo 31P and 1H NMR study.
Young RS, Chen B, Petroff OA, Gore JC, Cowan BE, Novotny EJ, Wong M, Zuckerman K
(1989) Pediatr Res 25: 27-31
MeSH Terms: Acetates, Animals, Animals, Newborn, Blood Glucose, Blood Pressure, Brain, Diazepam, Dogs, Electroencephalography, Glucose, Hydrogen-Ion Concentration, Lactates, Magnetic Resonance Spectroscopy, Phosphates, Phosphocreatine, Random Allocation, Seizures, Succinates, Valine
Show Abstract · Added December 10, 2013
It is assumed that when anticonvulsants arrest seizure, there is rapid return of brain high energy phosphates and brain lactate to control values. To test this hypothesis, diazepam was administered to neonatal dogs during flurothyl-induced seizure. In vivo 31P nuclear magnetic resonance spectroscopy disclosed that diazepam quickly arrested electrographic seizure and restored brain phosphocreatine and inorganic phosphate to baseline values. In contrast, in vivo 1H nuclear magnetic resonance spectroscopic measurements showed that arrest of seizure with diazepam did not return brain lactate to control values. The sustained increase in cerebral blood flow and prolonged elevation of brain lactate, acetate, valine, and succinate in the postictal period indicate that metabolic recovery of the brain occurs over an extended period of time after the normalization of EEG, phosphocreatine, and brain pH.
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19 MeSH Terms
Effects of cold exposure on inhibition by isoproterenol of release of alanine in the rat.
Yamada T, Shiota M, Sugano T
(1988) J Appl Physiol (1985) 64: 906-12
MeSH Terms: Alanine, Aminooxyacetic Acid, Animals, Cold Temperature, Cyclic AMP, Female, Hindlimb, Isoproterenol, Lactates, Muscles, Oxygen Consumption, Perfusion, Pyruvates, Rats, Rats, Inbred Strains, Valine
Show Abstract · Added December 10, 2013
The effects of isoproterenol on the release of alanine during perfusion with pyruvate and valine were studied in perfused hindlimbs from rats that had been kept for 5 or 20 days at 4 degrees C. In hindlimbs perfused with Krebs bicarbonate buffer in a flow-through mode, the rate of release of alanine during perfusion with 2 mM pyruvate plus 5 mM valine was 250 nmol.min-1.leg-1, a rate that is comparable with that reported in hindlimbs perfused with complex medium. Neither the pyruvate-stimulated nor valine plus pyruvate-stimulated rates of release of alanine changed after 20 days of exposure to cold. Isoproterenol inhibited the release of alanine during perfusion with pyruvate, with valine, and with valine plus pyruvate in hindlimbs from a control group of rats. However, in hindlimbs from cold-exposed groups, isoproterenol failed to inhibit the release of alanine during perfusion with valine plus pyruvate and stimulated the release of alanine during perfusion with valine. Aminooxyacetate inhibited the effects of valine, pyruvate, and isoproterenol. The results obtained suggested that cold exposure decreases the responses to isoproterenol of the mechanism of alanine release and causes an increased supply of alanine to the liver.
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16 MeSH Terms
Comparison of deuterated leucine, valine, and lysine in the measurement of human apolipoprotein A-I and B-100 kinetics.
Lichtenstein AH, Cohn JS, Hachey DL, Millar JS, Ordovas JM, Schaefer EJ
(1990) J Lipid Res 31: 1693-701
MeSH Terms: Adult, Apolipoprotein A-I, Apolipoprotein B-100, Apolipoproteins A, Apolipoproteins B, Deuterium, Humans, Kinetics, Leucine, Lipoproteins, Lysine, Valine
Show Abstract · Added March 20, 2014
The production rates of apolipoprotein (apo)B-100 in very low density lipoprotein and in low density lipoprotein and apolipoprotein A-I in high density lipoprotein were determined using a primed-constant infusion of [5,5,5,-2H3]leucine, [4,4,4,-2H3]valine, and [6,6-2H2,1,2-13C2]lysine. The three stable isotope-labeled amino acids were administered simultaneously to determine whether absolute production rates calculated using a stochastic model were independent of the tracer species utilized. Three normolipidemic adult males were studied in the constantly fed state over a 15-h period. The absolute production rates of very low density lipoprotein apoB-100 were 11.4 +/- 5.8 (leucine), 11.2 +/- 6.8 (valine), and 11.1 +/- 5.4 (lysine) mg per kg per day (mean +/- SDM). The absolute production rates for low density lipoprotein apoB-100 were 8.0 +/- 4.7 (leucine), 7.5 +/- 3.8 (valine), and 7.5 +/- 4.2 (lysine) mg per kg per day. The absolute production rates for high density lipoprotein apoA-I were 9.7 +/- 0.2 (leucine), 9.4 +/- 1.7 (valine, and 9.1 +/- 1.3 (lysine) mg per kg per day. There were no statistically significant differences in absolute synthetic rates of the three apolipoproteins when the plateau isotopic enrichment values of very low density lipoprotein apoB-100 were used to define the isotopic enrichment of the intracellular precursor pool. Our data indicate that deuterated leucine, valine, or lysine provided similar results when used for the determination of apoA-I and apoB-100 absolute production rates within plasma lipoproteins as part of a primed-constant infusion protocol.
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12 MeSH Terms
Hemoglobin Hofu (beta 126 Val is replaced by Glu) in a black American.
Russo FM, John ME, Waterman MR, Simon LM, Sheehan RG
(1979) Hemoglobin 3: 83-6
MeSH Terms: African Continental Ancestry Group, Amino Acid Sequence, Electrophoresis, Cellulose Acetate, Glutamates, Hemoglobin A, Hemoglobins, Abnormal, Humans, Male, Middle Aged, United States, Valine
Added February 12, 2015
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11 MeSH Terms
Molecular aspects of sickle cell disease.
Waterman MR, Cottam GL
(1976) Angew Chem Int Ed Engl 15: 749-57
MeSH Terms: Anemia, Sickle Cell, Electron Spin Resonance Spectroscopy, Erythrocytes, Gels, Glutamates, Hemoglobin A, Hemoglobin, Sickle, Kinetics, Macromolecular Substances, Microscopy, Electron, Oxygen, Protein Conformation, Thermodynamics, Valine, X-Ray Diffraction
Added February 12, 2015
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15 MeSH Terms