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X Parés

Publications and source records attributed to X Parés.

66 records · Page 4Linked to original sources
PubMed1984

Organ specific alcohol metabolism: placental chi-ADH.

Human placenta contains a single detectable isozyme of alcohol dehydrogenase that has been isolated and characterized. It migrates toward the anode on starch gel electrophoresis and can be stained with pentanol but not ethanol as substrate. Its kinetic and molecular characteristics are identical with those of the recently discovered chi-ADH (Class III) isozyme from human liver. Placental ADH is present in the cytosol of this organ in small amounts, 6 mg/kg fresh tissue. It oxidizes ethanol very slowly--even at ethanol concentrations that would reflect intoxication when found in serum. Thus, placental alcohol dehydrogenase cannot play a significant role in the ethanol metabolism of pregnant women.

Alcohol Dehydrogenase↗
PubMed1984

The properties of the interaction between bovine pancreatic ribonuclease a and mononucleotides supports the existence of several binding sub-sites in the enzyme.

The binding of 5'AMP, 5'GMP, 5'CMP, 3'CMP and Cl6RMP to RNAase A was studied by means of the gel filtration technique. It was found that only one molecule of 3'CMP binds strongly to the enzyme although a very unspecific binding is also present. The interaction of 5'AMP and 5'GMP with the enzyme shows one strong binding site and several weak binding sites, whereas two molecules of 5'CMP bind to RNAase A with equal strength. Cl6RMP shows an anomalous behaviour as both split peaks and troughs are found in the chromatogram. The Ka values for 3'CMP and the strong binding site of 5'AMP and 5'GMP are very similar whereas that for the two binding sites of 5'CMP is smaller (about 2.2 X 10(-4)M-1 and 0.5 X 10(-4)M-1, respectively at pH 5.5, I = 0.01 and 25 degrees C). The results are in general agreement with the known multiplicity of ligand-binding subsites in RNAase A.

Animals↗
PubMed1983

Purification and partial characterization of a rat retina alcohol dehydrogenase active with ethanol and retinol.

Homogeneous alcohol dehydrogenase (ADH) from rat retina was obtained by chromatography on DEAE-Sepharose and AMP-hexane-Sepharose. The enzyme is a dimer of Mr congruent to 80000 and oxidizes ethanol using NAD+ as a cofactor. Careful activity determinations demonstrate unambiguously that rat retina ADH is active with retinol as a substrate. This result opens the question about the role of retina ADH in the visual cycle.

Alcohol Dehydrogenase↗
PubMed1981

Simian liver alcohol dehydrogenase: isolation and characterization of isoenzymes from Macaca mulatta.

Like human liver alcohol dehydrogenase, that of Macaca mulatta can be purified and separated into anodic and cathodic pyrazole-insensitive and cathodic pyrazole-sensitive enzyme forms. Their inhibition by 4-methylpyrazole and their substrate specificities are analogous to those observed for the corresponding isoenzymes of human liver. However, on the basis of data available so far, the physiochemical and compositional characteristics, i.e., molecular weight, zinc content, and dimeric structure, of all simian alcohol dehydrogenase forms are virtually identical with those of other mammalian alcohol dehydrogenases studied up to now. Zinc is essential for their enzymatic function, as demonstrated by inhibition with chelating agents.

Alcohol Dehydrogenase↗
PubMed1981

1H-NMR studies on the binding subsites of bovine pancreatic ribonuclease A.

The titration curves of the C-2 histidine protons of an RNAase derivative (a covalent derivative obtained by reaction of bovine pancreatic RNAase A (EC 3.1.27.5) with 6-chloropurine 9-beta-D-ribofuranosyl 5'-monophosphate) were studied by means of 1H-NMR spectroscopy at 270 MHz. The interaction of natural (5'AMP, 5'GMP, 5'IMP) and halogenated purine mononucleotides (cl6RMP, br8AMP) with RNAase A was also monitored by using the same technique. The slight change observed in the pK values of the active centre histidine residues of the RNAase derivative, with respect to those in the native enzyme, can be considered as evidence that the phosphate of the label does not interact directly either with His-12 or 119 in the p1 site, but the p2 site as proposed previously (Parés, X., Llorens, R., Arús, C. and Cuchillo, C.M. (1980) Eur. J. Biochem. 105, 571--579). Lys-7 and/or Arg-10 are proposed as part of the p2 phosphate-binding subsite. The pK values of His-12 and 119 and the shift of an aromatic resonance of the native enzyme found on interaction with some purine nucleotides, can be interpreted by postulating that the interaction of 5'AMP, 5'GMP and 5'IMP takes place not only in the so-called purine-binding site B2R2p1 but also in the primary pyrimidine-binding site B1R1 and p0 of RNAase A.

Animals↗
PubMed1981

Simian liver alcohol dehydrogenase: isolation and characterization of isoenzymes from Saimiri sciureus.

The alcohol dehydrogenase (ADH) of squirrel monkey liver can be purified and separated into pyrazole-insensitive and pyrazole-sensitive isoenzymes by affinity chromatography. This is the first demonstration of two functionally distinct classes of ADH in a species other than man. The inhibition of the two enzyme fractions by 4-methylpyrazole is analogous to that observed for the corresponding isoenzymes of human liver. Similarly, the substrate specificity of the pyrazole-insensitive form is more limited and its Km for ethanol (4 mM at pH 7.5) and acetaldehyde (11 mM at pH 7.0) is larger than that of the pyrazole-sensitive isoenzymes. However, their physicochemical and compositional characteristics, i.e., molecular weight, zinc content, and dimeric structure, are all virtually identical with those of other mammalian alcohol dehydrogenases studied thus far. Zinc is essential for the enzymatic function of both molecular forms as demonstrated by inhibition with chelating agents.

Alcohol Oxidoreductases↗
PubMed1980

The reaction of bovine pancreatic ribonuclease A with 6-chloropurineriboside 5'-monophosphate. Evidence on the existence of a phosphate-binding sub-site.

The chemical modification of bovine pancreatic ribonuclease A by 6-chloropurine 9-beta-D-ribofuranosyl 5'-monophosphate was studied under several reaction conditions. The reaction, at pH 7.3, 40 degrees C and a nucleotide: enzyme molar ratio of 60, showed a high degree of specificity in comparison to those corresponding to the base or the nucleoside. The main derivative was isolated by means of CM-cellulose chromatography. Subtilisin cleavage of this derivative showed that the substitution had taken place in the S-peptide moiety. Tryptic digestion of the S-peptide indicated that a lysine residue had been modified. Enzymatic and physico-chemical considerations showed that the actual site of reaction was the alpha-amino group of Lys-1. The structural and kinetic properties of the derivative are consistent with the existence of a phosphate-binding sub-site near the N-terminal region of the enzyme.

Amino Acids↗
PubMed1980

Reaction of bovine pancreatic ribonuclease A with 6-chloropurine riboside 5'-monophosphate. Nuclear magnetic resonance studies of the corresponding S-peptide.

The n.m.r. spectra of native S-peptide and of S-peptide II, a derivative obtained after reaction of bovine pancreatic ribonuclease A with 6-chloropurine riboside 5'-monophosphate, both in D2O and in urea-d4, were obtained with a 270 MHz Fourier transform spectrometer. From these spectra it was possible to assign most of the proton resonances of the peptide and the position of the labelling group, the alpha-NH2 of Lys-1, was also deduced.

Animals↗
PubMedDate not supplied

Properties of rat retina alcohol dehydrogenase.

The rat eye fraction, including retina, pigment epithelium and choroid, contains an alcohol dehydrogenase (ADH) isoenzyme that is not present in rat liver. Starch gel electrophoresis of retina ADH shows an anodic band that can be visualized by activity staining, using either ethanol or pentanol as substrates. Ethanol is a poor substrate (Km: 336 mM, at pH 10.0) for the purified retina ADH which prefers long chain, 2-unsaturated and aromatic alcohols. The enzyme has a pH optimum of 10.0 for ethanol oxidation and it is inhibited by 4-methylpyrazole (KI: 10 microM). Electrophoretic and kinetic properties clearly differentiate the retina ADH from the hepatic cathodic ADH isoenzymes and from an anodic chi-ADH-like form that we have also detected in rat liver. At the pH and ethanol concentrations found "in vivo," retina ADH can oxidize ethanol to an appreciable extent. The subsequent production of acetaldehyde and redox change may be responsible for visual disorders during alcohol intoxication.

Alcohol Dehydrogenase↗
PubMedDate not supplied

Helicobacter pylori infection decreases gastric alcohol dehydrogenase activity and first-pass metabolism of ethanol in man.

BACKGROUND/AIMS: Ethanol is metabolized by alcohol dehydrogenase in the human stomach. This metabolism contributes to the so-called first-pass metabolism of ethanol which is affected by gender, medication, and morphological alterations of the gastric mucosa. Recently, it has been shown that Helicobacter pylori is capable to oxidize ethanol to acetaldehyde in vitro. Since H. pylori also injures gastric mucosa, the present study examines the effect of this bacterium on gastric alcohol dehydrogenase activity and systemic availability of ethanol in vivo. METHODS: Thirteen volunteers (7 men and 6 women, aged 18-52 years) with gastric H. pylori infection diagnosed by a positive CLO test and positive gastric histology received ethanol (0.225 g/kg) either orally or intravenously before and after H. pylori elimination to determine systemic availability of ethanol. In addition, gastric biopsy specimens were taken from all subjects before and after H. pylori elimination for histological assessment of mucosal alterations and determinations of gastric alcohol dehydrogenase activity and phenotype of the enzyme. RESULTS: In the presence of H. pylori the first-pass metabolism of ethanol was found to be significantly reduced (625 +/- 234 vs. 1,155 +/- 114 mg/dl/min, p = 0.046). This reduction of first-pass metabolism of ethanol was associated with a significant decrease in alcohol dehydrogenase activity (4.8 +/- 1.5 vs. 12.1 +/- 2.3 nmol/mg protein x min, p < 0.05) and an increase in the severity of mucosal damage as determined by a histological score (p < 0.05). CONCLUSIONS: H. pylori infection leads to gastric mucosal injury which is associated with a decrease in gastric alcohol dehydrogenase activity and first-pass metabolism of ethanol. Ethanol metabolism by H. pylori does not play an important role in vivo. However, gastric morphology is one important factor determining systemic availability of ethanol in man.

Adolescent↗
PubMedDate not supplied

Action of metadoxine on isolated human and rat alcohol and aldehyde dehydrogenases. Effect on enzymes in chronic ethanol-fed rats.

Metadoxine (pyridoxine-pyrrolidone carboxylate) has been reported to accelerate ethanol metabolism. In the present work we have investigated the effect of metadoxine on the activities of isolated alcohol and aldehyde dehydrogenases from rat and man, and on the activity of these enzymes in chronic ethanol-fed rats. Our results indicate that in vitro metadoxine does not activate any of the enzymatic forms of alcohol dehydrogenase (classes I and II) or aldehyde dehydrogenase (low-Km and high-Km, cytosolic and mitochondrial). At concentrations higher than 0.1 mM, metadoxine inhibits rat class II alcohol dehydrogenase, although this would probably not affect the physiological ethanol metabolism. Chronic ethanol intake for 5 weeks results in a 25% decrease of rat hepatic alcohol dehydrogenase (class I) activity as compared with the pair-fed controls. The simultaneous treatment with metadoxine prevents activity loss, suggesting that the positive effect of metadoxine on ethanol metabolism can be explained by the maintenance of normal levels of alcohol dehydrogenase during chronic ethanol intake. No specific effect of chronic exposure to ethanol or to metadoxine was detected on rat aldehyde dehydrogenase activity.

Alcohol Dehydrogenase↗