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At least 19 recordsLinked to original sources
PubMed1978

The aromatic alcohol dehydrogenases in Pseudomonas putida N.C.I.B. 9869 grown on 3,5-xylenol and p-cresol.

Whole cells of Pseudomonas putida N.C.I.B 9869, when grown on either 3,5-xylenol or p-cresol, oxidized both m- and p-hydroxybenzyl alcohols. Two distinct NAD+-dependent m-hydroxybenzyl alcohol dehydrogenases were purified from cells grown on 3,5-xylenol. Each is active with a range of aromatic alcohols, including both m- and p-hydroxybenzyl alcohol, but differ in their relative rates with the various substrates. An NAD+-dependent alcohol dehydrogenase was also partially purified from p-cresol grown cells. This too was active with m- and p-hydroxybenzyl alcohol and other aromatic alcohols, but was not identical with either of the other two dehydrogenases. All three enzymes were unstable, but were stabilized by dithiothreitol and all were inhibited with p-chloromercuribenzoate. All were specific for NAD+ and each was shown to catalyse conversion of alcohol into aldehyde.

Alcohol Oxidoreductases↗
PubMed1976

Isotope effects and structure-reactivity correlations in the yeast alcohol dehydrogenase reaction. A study of the enzyme-catalyzed oxidation of aromatic alcohols.

Steady-state kinetic parameters for the yeast alcohol dehydrogenase catalyzed oxidation of a series of parasubstituted benzyl alcohols-1, 1-h2 and -1, 1-d2 by NAD+ are reported. Catalytic constants have been found to be characterized by large deuterium isotope effects: kH/kD=4.8, p-Br; 4.2, p-Cl; 3, 4, p-H; 4, 2, p-CH3; 3, 2, p-CH3O. The observed isotope effects on k(cat)/K(A), K(A), and K(B), where K(A) and K(B) are Michaelis constants for NAD+ and alcohol, indicate a borderline rapid equilibrium-steady-state kinetic mechanism involving the random addition of substrate and coenzyme to enzyme. With the exception of p-CH3 and possible p-CH3O substituted benzyl alcohol, k(cat) is concluded to represent a single, rate-limiting hydrogen transfer step. A multiple linear regression analysis of the combined data for benzaldehyde reduction (Klinman, J.P. (1972), J. Biol. Chem. 247, 7977-7987, expanded to include p-CH(CH3) 2-substituted benzaldehyde) and benzyl alcohol oxidation has been carried out to determine the contribution of electronic, hydrophobic, and steric effects to k(cat) and substrate binding. Benzaldehyde binding is concluded to depend on electronic substituent effects as previously reported [log 1/K(ald)=(-0.92 +/- 0.18)sigma+-(0.80 +/- 0.067)], whereas benzyl alcohol binding correlates with substrate hydrophobicity [(log 1/K(alc)=(0.60 +/- 0.14) log P -(1.2 +/- 0.12)]. In the case of benzyl alcohol oxidation, k(cat) is independent of electronic and steric effects; the best of seven equations indicates a small negative dependence of k(cat) on hydrophobicity, which is within experimental error or zero [log k(o)=(-0.075 +/- 0.25) log P -(0.65 +/- 0.19)]. Data for benzaldehyde reduction are correlated at the 99% significance level by a single variable equation [(log k(R)=(2.1 +/- 0.37) sigma+-(0.093 +/- 0.14)] and a two variable equation [(log k(R)=(1.9 +/- 0.33) sigma+ + (0.46 +/- 0.20) log P-(0.46 +/- 0.20)]; these equations indicate (a) a large dependence on electronic substituent as reported previously and (b) a possible role for hydrophobic factors in facilitating catalysis. As the result of the observed hydrophobic substituent effects, different ground-state interactions are suggested for the binding of benzaldehydes and benzyl alcohols. Electronic substituent effects lead to the conclusion that there is little or no change in charge at C-1 of substrate at the transition state, relative to alcohol in the ground state. The significance of these effects to the detailed properties of the hydrogen transfer step is discussed.

Alcohol Oxidoreductases↗
PubMed1978

Alcohol-oxidizing enzymes in 13 Drosophila species.

Starch and polyacrylamide gel electrophoresis were used to ascertain the substrate specificities of alcohol-oxidizing enzymes in 13 Drosophila species. The substrates used were a variety of long- and short-chain aliphatic alcohols, one aromatic alcohol, and benzaldehyde. Only one enzyme (product of a single-gene locus) showed significant NAD+-dependent alcohol dehydrogenase activity with short-chain aliphatic alcohols. The 13 species, belonging to four different Drosophila groups, all showed a similar complement of alcohol-oxidizing enzymes, although differences in electrophoretic mobility and in levels of activity existed from species to species. These findings are relevant to the adaptation of Drosophila to alcohol environments.

Alcohol Oxidoreductases↗
PubMed1978

[Electrophoretic analysis of substrate specificity of wheat alcohol dehydrogenases].

Electrophoresis in polyacrylamide gel slabs has been used to study the isoform composition and substrate specificity of alcohol dehydrogenases in the embryo and young seedlings of the diploid wheat Triticum monococcum L., the tetraploid T. dicoccon (Schrank) Schuebl and the hexaploid T. spelta L. Three alcohol dehydrogenases of different substrate specificity and developmental pattern were distinguished: a) the NAD-dependent alcohol dehydrogenase, catalyzing the oxidation of different primary and secondary aliphatic and aromatic alcohols, as well as certain compounds with several hydroxyl groups (tris, triethanolamin) and revealing, after electrophoresis, one major band in the diploid wheat and three bands in both polyploid wheats; b) the NADP-dependent aromatic alcohol dehydrogenase (substrate--cinnamic alcohol), revealing, after electrophoresis, one major fast moving band in the diploid wheat and two bands in polyploid wheats; c) an aromatic alcohol dehydrogenase (2-3 bands after electrophoreis) with no specificity to the cofactors (NAD or NADP).

Alcohol Oxidoreductases↗
PubMed1975

Effect of pH on the liver alcohol dehydrogenase reaction.

New transient kinetic methods, which allow kinetics to be carried out under conditions of excess substrate, have been employed to investigate the kinetics of hydride transfer from NADH to aromatic aldehydes and from aromatic alcohols to NAD+ as a function of pH. The hydride transfer rate from 4-deuterio-NADH to beta-naphthaldehyde is nearly pH independent from pH 6.0 to pH 9.9; the isotope effect is also pH independent with kappa-H/kappaD congruent to 2.3. Likewise, the rate of oxidation of benzyl alcohol by NAD+ changes little with pH between pH 8.75 and pH 5.9; the isotope effect for this process is between 3.0 and 4.4. Earlier substituent effect studies on the reduction of aromatic aldehydes were consistent with electrophilic catalysis by either zinc or a protonic acid. The pH independence of hydride transfer is consistent with electrophilic catalysis by zinc since such catalysis by protonic acid (with a pK between 6.0 and 10.0) would show strong pH dependence. However, protonic acid catalysis cannot be excluded if the pKa of the acid catalyst in the ternary NADH-E-RCOH complex were smaller than 6.0 or smaller than 10.0. The two kinetic parameters changing significantly with pH are the kinetic binding constant for ternary complex formation with aromatic alcohol and the rate of dissociation of aromatic alcohols from enzyme. This is consistent with base-catalyzed removal of a proton from alcohol substrated and consequent acid catalysis of protonation of a zinc-alcoholate complex. The equilibrium constant for hydride transfer from benzaldehyde to benzyl alcohol at pH 8.75 is K-eq equals kappa-H/kappa-H equals 42; this constant has important consequences concerning subunit interactions during liver alcohol dehydrogenase catalysis.

Alcohol Oxidoreductases↗
PubMed2025

Quorum sensing in Saccharomyces cerevisiae brewing strains: effects of 2-phenylethanol on proteomic, lipidomic, and metabolomic profile.

Quorum sensing (QS) is a known mechanism by which microbial populations adjust gene expression and coordinate community-wide social behaviors based on the proximate population density. This regulatory system has garnered significant interest in both scientific research and the food industry. However, a central question remains whether industrial strains of Saccharomyces cerevisiae, the yeast species predominantly utilized in brewing, employ quorum signalling mechanisms similar to those observed in laboratory strains and other fungi. Despite the potential relevance of microbial social behavior regulators to brewing practices, studies examining QS in Saccharomyces spp. are limited. In this investigation, three industrial brewing strains of S. cerevisiae were cultivated on SLAD (nitrogen-restrictive) and SHAD (nitrogen-sufficient) agar media supplemented with 200 μM of the aromatic alcohol 2-phenylethanol (2-PE) over 72 h at 24°C. Subsequent analyses of the harvested biomass included proteomic, lipidomic, and metabolomic assessments. Results indicated that two of the industrial strains showed minimal differences in their profiles upon exposure to 2-PE, while the third strain exhibited significant differences. These findings imply that the impact of the QS molecule 2-PE on the proteome, lipidome, and metabolome of industrial S. cerevisiae may be strain-specific rather than universally applicable to the species.

Quorum Sensing↗
PubMed1976

Microbial oxidation of methane and methanol: crystallization and properties of methanol dehydrogenase from Methylosinus sporium.

Obligate methylotrophs are divisible into two types on the basis of ultrastructural biochemical characteristics. Both groups possess a soluble phenazine methosulfate (PMS)-dependent methanol dehydrogenase. In addition, particulate PMS-dependent methanol dehydrogenase and PMS-independent methanol oxidase have been found in the type I membrane group. A procedure was developed for the crystallization of methanol dehydrogenase from the soluble fraction of the type II obligate methylotroph Methylosinus sporium. This is the first report of a crystalline methanol dehydrogenase from a methylotrophic bacterium. The crystallized enzyme is homogeneous as judged by ultracentrifugation and by acrylamide gel electrophoresis. In the presence of an electron acceptor (phenazine or phenazinium compound) and an activator (ammonium compound), the crystallized enzyme catalyzed the oxidation of primary alcohols and formaldehyde. Secondary, tertiary, and aromatic alcohols were not oxidized. The molecular weight of the enzyme as estimated by gel filtration is approximately 60,000, and as estimated by sedimentation equilibrium analysis it is 62,000. The sedimentation constant (S20,W) is 2.9. The subunit size determined by sodium dodecyl sulfate-gel electrophoresis is approximately 60,000. The amino acid composition and spectral properties of the enzyme are also presented. Antisera prepared against the crystalline enzyme are nonspecific, they cross-reacted and inhibited isofunctional enzymes from other obligate methylotrophic bacteria.

Alcohol Oxidoreductases↗
PubMed1978

Microbial oxidation of methane and methanol: crystallization of methanol dehydrogenase and properties of holo- and apomethanol dehydrogenase from Methylomonas methanica.

Procedures are described for the purification and crystallization of methanol dehydrogenase from the soluble fraction of the type I obligate methylotroph Methylomonas methanica strain S1. The crystallized enzyme is homogeneous as judged by acrylamide gel electrophoresis and ultracentrifugation. The enzyme had a high pH optimum (9.5) and required ammonium salt as an activator. In the presence of phenazine methosulfate as an electron acceptor, the enzyme catalyzed the oxidation of primary alcohols and formaldehyde. Secondary, tertiary, and aromatic alcohols were not oxidized. The molecular weight as well as subunit size of methanol dehydrogenase was 60,000, indicating that it is monomeric. The sedimentation constant (s(20,w)) was 3.1S. The amino acid composition of the crystallized enzyme is also presented. Antisera prepared against the crystalline enzyme were nonspecific; they cross-reacted with and inhibited the isofunctional enzyme from other obligate methylotrophic bacteria. The crystalline methanol dehydrogenase had an absorption peak at 350 nm in the visible region and weak fluorescence peaks at 440 and 470 nm due to the presence of a pteridine derivative as the prosthetic group. A procedure was developed for the preparation of apo-methanol dehydrogenase. The molecular weights, sedimentation constants, electrophoretic mobilities, and immunological properties of apo- and holo-methanol dehydrogenases are identical. Apo-methanol dehydrogenase lacked the absorption peak at 350 nm and the fluorescence peaks at 440 and 470 nm and was catalytically inactive. All attempts to reconstitute an active enzyme from apo-methanol dehydrogenase, using various pteridine derivatives, were unsuccessful.

Alcohol Oxidoreductases↗
PubMed1979

An enzyme-polymer film prepared with the use of poly(vinyl alcohol) bearing photosensitive aromatic azido groups.

Photochemical reaction of poly(vinyl alcohol) bearing aromatic azido groups was applied for immobilization of beta-glucosidase (beta-D-glucoside glucohydrolase, EC 3.2.1.21.) in poly(vinyl alcohol) film. Photo-crosslinking and immobilization reactions proceeded by light irradiation for 25 min in air. The immobilized enzyme showed approx. 40% of its native enzyme activity with an apparent Michaelis constant of 3.9 mM. The Michaelis constant of the native enzyme was 2.3 mM. Some properties of the immobilized and native enzyme are compared.

Azides↗
PubMed2026

Chemical and sensory profiling of fermented, washed, and artificially flavored coffee beans: Insights into flavour quality, authenticity, and food safety implications.

This study establishes an integrated framework combining chemical profiling, sensory analysis, and molecular mechanism evaluation to compare flavour quality and authenticity among fermented, washed, and artificially flavored coffees. GC&#xa0;&#xd7;&#xa0;GC-TOF-MS and UHPLC-HRMS showed that fermented samples had markedly higher ester and aromatic alcohol levels (total esters 74.5&#xa0;&#xb1;&#xa0;7.8&#xa0;mg&#xa0;kg-1; phenylethanol 27.5&#xa0;&#xb1;&#xa0;3.2&#xa0;mg&#xa0;kg-1, p&#xa0;<&#xa0;0.01), enhancing fruity-floral notes. Washed coffees contained the highest organic acid concentrations (45.2&#xa0;&#xb1;&#xa0;3.8&#xa0;mg&#xa0;kg-1, p&#xa0;<&#xa0;0.01), supporting brightness and umami. Artificially flavored coffees exhibited elevated exogenous aromatics (vanillin 21.5&#xa0;&#xb1;&#xa0;3.1&#xa0;mg&#xa0;kg-1) but significantly fewer Maillard products (p&#xa0;<&#xa0;0.05) and reduced flavour retention (55% after 14 days). Molecular docking revealed higher theoretical binding affinities for naturally generated compounds, suggesting a potential molecular basis for their greater sensory persistence. The framework supports constructing coffee quality fingerprints and verifying flavour authenticity.

Flavoring Agents↗
PubMed1975

Mammalian liver alcohol dehydrogenases.

Literature on the properties of liver alcohol dehydrogenase (ADH) from man, horse and rat is reviewed and discussed under two major headings: 1) physical and chemical properties of ADH and 2) structure-function relationship in isoenzymes. Under the first heading are discussed: molecular weight, subunit composition catalytic sites per molecule, sulfhydryl groups, end groups, amino acid composition, role of Zn++ in the structure and function, coenzyme specificity and binding, conformational changes, substrate specificity, catalytic mechanism and recent results from x-ray crystallography of horse liver ADH. The physicochemical properties of ADH from man, horse and rat are for the most part similar. All three enzymes have identical molecular weights, similar amino acid compositions, consist of two subunits, and are all metalloenzymes containing Zn++: horse and human ADH contain one coenzyme binding site per subunit; no results are available for the rat ADH. ADH catalyses interconversion of a large variety of saturated and unsaturated aliphatic and aromatic alcohols and the corresponding aldehydes and ketones utilizing NAD(H). The physiological role of ADH is uncertain. ADH readily combines with reduced coenzymes to form binary complexes with low dissociation constants (10-7 to 10-8M); in the ternary complexes with coenzymes and substrate-competitive inhibitors, these constants are even lower. In the presence of suitable inhibitors, the enzymes can be titrated by coenzymes employing fluorometric and spectrophotometric procedures. The rate of the overall reaction catalyzed by ADH is determined by the dissociation rates of coenzymes, the slowest steps in the reaction sequence. Under the second heading are discussed: liver ADH isoenzymes of horse, man, rat, rhesus monkey and other species, and the significance of steroid activity which accounts for the distinct substrate specificity of some isoenzymes. ADH from horse liver is a heterogeneous enzyme consisting of subunits of distinct substrate specificity and primary structure. The difference in the amino acid sequence between subunit E (active with classical ADH substrates, but not with steroids) and subunit S (active also with steroids) amounts to six amino acids out of 374. Human ADH is also heterogeneous, and at least five genes code for polypeptides which, by dimerization, form different isoenzymes. Experimental evidence suggests that rat ADH is a single unique protein which, like horse liver ADH, SS, is active with steroids. The physiological significance of steroid activity of ADHs is unknown. (Four tables with comparative data and one figure are presented).

Alcohol Oxidoreductases↗
PubMed1978

Biochemical characterization of an aryl acetic ester hydrolase isolated from human monocytes.

A carboxylic-ester hydrolase was isolated from the leukocytes of a patient with myelomonocytic leukemia. Its relative molecular mass as estimated by sucrose density-gradient sedimentation is about 70 000. The purified enzyme is specific for acetyl esters of aromatic alcohols. It is inhibited by fluoride, but insensitive to eserine or p-chloromercuriphenylsulfonate. Hydrolysis of 1-naphthyl acetate was optimal above pH 6.0; of o-nitrophenyl acetate, above 8.0. The common catalytic site for the two types of substrates on the enzyme was confirmed by competitive inhibition data.

Acetates↗
PubMed1979

[About the antimicrobial activity of substituted aromatic aldehydes and alcohols (author's transl)].

In the scope of our research about the antimicrobial activity of serveral chemicals a number of substituted benzaldehydes and benzylalcohols was investigated under standardized conditions following the method of DGHM (German Society of Hygiene and Microbiology) against bacteria, dermatophytes and moulds. The germicidal activity, demonstrated by the suspension test, is generally low except under special conditions (low or high pH-value). The germistatic activity, demonstrated by the MIC-test, is much higher than the germicidal effect (figs. 1--4). The relation structure-germistatic activity is discussed.

Anti-Bacterial Agents↗