[Oxidative stress and diabetes: role in the development of chronic complications]

"Oxidative stress" resulting both from over-production of reactive oxygen radicals and decreased efficiency of antioxidant defenses is now considered a factor contributing to the determination of chronic diabetic complications. The strict relations between the known pathogenetic factors involved in the development of these complications (non enzymatic protein glycation, activation of polyol pathway, lipidic changes, haematostatic abnormalities) and oxidative stress are examined in the light of the most recent research studies. The latest therapeutical approaches aiming at an increase in antioxidant defenses, and a reduction of oxidant are reported.

Gas chromatographic whole-cell fatty acid analysis as an aid for the identification of mixed mycobacterial cultures

Gas chromatographic analysis of whole-cell fatty acids, secondary alcohols and mycolic acid cleavage products could be a useful technique in checking mixed mycobacterial cultures. The mixed cultures were confirmed when species-specific compounds of different mycobacterial species were detected in the same chromatogram.

Perinatal development of amine, alcohol and phenol sulfoconjugations in the rat

Development of the sulfoconjugating activities for amine, alcoholic and phenolic compounds was studied in hepatic 105,000 g supernatants of fetal and newborn rats. All activities in the fetus at the late stage of pregnancy were negligible or very low when compared with those of the adult female level. Amine and alcohol sulfoconjugating activities were low 2 days after birth, increased with age, and attained the adult female level 17 days after birth. In contrast, phenol sulfoconjugating activity was nearly half the level of adult female rats in the neonates 2 days after birth and was relatively constant before maturation. There were no sex-related differences in any of the activities in the immature rats, but in adult animals the activities for amine and alcohol were higher in the females than in the males; the opposite was observed for phenol sulfoconjugation.

Identification of amino acids in HIV-2 integrase involved in site-specific hydrolysis and alcoholysis of viral DNA termini

The human immunodeficiency virus integrase (HIV IN) protein cleaves two nucleotides off the 3' end of viral DNA and subsequently integrates the viral DNA into target DNA. IN exposes a specific phosphodiester bond near the viral DNA end to nucleophilic attack by water or other nucleophiles, such as glycerol or the 3' hydroxyl group of the viral DNA molecule itself. Wild-type IN has a preference for water as the nucleophile; we here describe a class of IN mutants that preferentially use the 3' hydroxyl group of viral DNA as nucleophile. The amino acids that are altered in this class of mutants map near the putative active-site residues Asp-116 and Glu-152. These results support a model in which multiple amino acid side-chains are involved in presentation of the (soluble) nucleophile. IN is probably active as an oligomeric complex, in which the subunits have non-equivalent roles; we here report that nucleophile selection is determined by the subunit that supplies the active site.

Alcohol dehydrogenase (ADH2) from a mutant strain of Candida guilliermondii A80-03: purification and characterization

Alcohol dehydrogenase ADH2 was purified twice from Candida guilliermondii strain A80-03, by ion exchange column chromatography on DEAE-Toyopearl 650M. The enzyme was a dimer of M(r) 98,500. ADH2 had a broad substrate specificity, oxidizing secondary alcohols as well as primary alcohols. The enzyme was sensitive to several inhibitors, such as metal chelators and thiol reagents. Kinetic studies suggested that ADH2 oxidized ethanol by an iso ordered sequential mechanism.

Tetrapropylammonium perruthenate as a mild and efficient oxidant for sensitive steroidal alcohols

Tetrapropylammonium perruthenate N-methylmorpholine N-oxide oxidation of steroidal alcohols is described. The reagent combination is mild and gave good yields of the corresponding ketones. Although the oxidation can generate ketones from 3-, 11-, 15-, 17-, and 20-hydroxy steroids, the oxidation of homoallylic alcohols proceeds in low yields. Finally, we observed that the oxidation reagents will convert 17 alpha-hydroxy-20-keto steroids to 17-keto systems in excellent yield.

Alcohol esterification reactions and mechanisms of snake venom 5'-nucleotide phosphodiesterase

In a previous study we have shown that snake venom 5'-nucleotide phosphodiesterase (SVP) catalyzes methanol-esterification reactions [García-Díaz, M., Avalos, M. & Cameselle, J. C. (1991) Eur. J. Biochem. 196, 451-457]. Now we have demonstrated that SVP catalyzes AMP transfer from ATP to propanol, ethanol, methanol, ethylene glycol, glycerol, 2-chloroethanol or 2,2-dichloroethanol. The AMP-O-alkyl ester products were identified by HPLC, enzyme analysis, ultraviolet and NMR spectroscopy. Those results show the potential of SVP as a tool to prepare 5'-nucleotide esters and agree with the formation of a covalent 5'-nucleotidyl-SVP intermediate susceptible to nucleophilic attack by short-chain (poly)alcohols as acceptors alternative to water. To test the kinetic influence of the solvent nucleophile in SVP mechanisms, initial rates of ATP solvolysis were assayed in different water/alcohol mixtures. Relatively high alcohol concentrations inactivated SVP but lower concentrations gave proportional rates of alcoholysis. An efficiency parameter (EA), defined as the ratio of the mole fraction of AMP-O-alkyl ester as a product to that of alcohol as an acceptor in water/alcohol mixtures, made possible the comparison of alcohols and water as AMP acceptors at low concentrations, as it could be reasoned that EA = 1 for water. Rates of hydrolysis (VH) of substrates yielding AMP and different leaving groups were also assayed. The higher EA and VH values corresponded, respectively, to those acceptors and leaving-group conjugate acids with lower pKa and higher polar-substituent constants (sigma*). The results support the occurrence of general acid-base catalysis in the active center of SVP and the identification of rate-limiting steps. A model is proposed for the mechanisms of SVP-catalyzed hydrolysis and alcoholysis which accounts for the influence of the acid-base properties of alcohols on the kinetic profile of SVP reaction sequences.

Alcohol production in submerged cashew pomace

The variations in the total titratable acidity, hydrogen ion concentration, reducing sugar, soluble solids and alcohol contents of the supernatant of the submerged cashew pomace in a non-aseptic condition were investigated. The crude fibre content of the pomace was also determined during fermentation. At intervals, the changes in microbial load in both the pomace and its supernatant were examined during the 14-day study. Fifty four percent of the total soluble solids (TSS) was utilised within 7 days of degradation while an increase of about 91% in the total titratable acidity occurred in the cashew pomace within the same period bringing its pH to 3.24. Acid hydrolysis of the pomace accounted for the relative high value of 2.15% TSS on the 8th day. Isolates of the genera Leuconostoc, Lactobacillus, Pediococcus, Aspergillus, Rhizopus and some yeast strains were obtained from the fresh pomace. The fungal colonies constituted about 76% of the population in the cashew pomace. The 86% drop in microbial population of the 8th day biodegraded pomace could be attributed to a decrease in nutrients of the substrate and the inhibitory effect of the organic acids produced during fermentation.

Formation of epoxyalcohols by a purified allene oxide synthase. Implications for the mechanism of allene oxide synthesis

The allene oxide synthase (hydroperoxide dehydrase) of flaxseed is a cytochrome P450 that exhibits an exceptionally high catalytic turnover (> or = 1000/s) for hydroperoxy substrates. In a previous study, using a crude extract of flaxseed, we detected a secondary activity that could offer an insight into the mechanism of the enzymatic transformation of hydroperoxides. We observed that the substrate 8R-hydroxy-15S-hydroperoxyeicosa-5,9,11,13,17-pentaenoic acid is converted not only to allene oxide, but also to epoxyalcohol derivatives (Brash, A. R., Baertschi, S. W., and Harris, T. M. (1990) J. Biol. Chem. 265, 6705-6712). The transformation of hydroperoxides to epoxyalcohols has been investigated extensively in other systems, and heterolytic or homolytic cleavage of the hydroperoxide is associated with characteristic rearrangements and stereochemistry of the epoxyalcohol products. Using the purified enzyme, we established that the epoxyalcohols are products of the allene oxide synthase. Their structures were determined by UV, gas chromatography-mass spectrometry, and NMR. The major epoxyalcohol is 8R,13R-dihydroxy-14R,15S-epoxyeicosa-5Z,9E ,11Z,17Z-tetraenoic acid, a trans-epoxide with an alpha-hydroxyl in the relative threo configuration. Two minor products are the corresponding 11E isomer and a cis-epoxide identified as 8R,13-dihydroxy-14S,15S-epoxyeicosa-5Z,9E,11E,++ +17Z-tetraenoic acid. Gas chromatography-mass spectrometry analysis of a reaction with [18O2]hydroperoxide substrate indicated complete retention of the hydroperoxy oxygens in the epoxyalcohol products. Mechanistic precedents support a homolytic hydroperoxide cleavage as the initial step in the synthesis of these epoxyalcohols. We suggest that the same process initiates allene oxide synthesis, a conclusion that is also most compatible with the known chemistry of cytochromes P450.

Nicotinoprotein [NAD(P)-containing] alcohol/aldehyde oxidoreductases. Purification and characterization of a novel type from Amycolatopsis methanolica

Extracts of Gram-positive bacteria like Rhodococcus rhodochrous, Rhodococcus erythropolis and Amycolatopsis methanolica, but not those of several Gram-negative ones, showed dehydrogenase activity for ethanol as well as for methanol when 4-nitroso-N,N-dimethylaniline (NDMA) was used as electron acceptor. Chromatography of extracts of the first two organisms revealed one activity for both substrates, that of A. methanolica two activities, one of which is able to oxidize methanol and has been purified (Bystrykh, L.V., Govorukhina, N.I., van Ophem, P.W., Hektor, H.J., Dijkhuizen, L. and Duine, J.A., unpublished results). The other, indicated as NDMA-dependent alcohol dehydrogenase (NDMA-ADH), was purified to homogeneity. It is a trimeric enzyme consisting of subunits of 39 kDa and one firmly bound NAD as cofactor. Although NDMA-ADH shows structural similarity with the long-chain, zinc-containing, NAD(P)-dependent alcohol dehydrogenases with respect to the N-terminal sequence up to residue 41 (56% identity with horse liver alcohol dehydrogenase), the enzymes are catalytically different since NDMA-ADH is unable to use NAD(P)(H) as a coenzyme and NAD(P)-dependent alcohol dehydrogenases are inactive with NDMA (in the absence of NAD). Comparison of the NDMA-ADH properties with those of the methanol-oxidizing enzyme of A. methanolica, Mycobacterium gastri and Bacillus methanolica C1, and formaldehyde dismutase of Pseudomonas putida F61 revealed large differences in structural as well as catalytic properties, in spite of the fact that all are nicotinoproteins [enzymes which have bound NAD(P) as a cofactor]. It is concluded, therefore, that NDMA-ADH is a novel type of nicotinoprotein alcohol dehydrogenase.

A symmetric inhibitor binds HIV-1 protease asymmetrically

Potential advantages of C2-symmetric inhibitors designed for the symmetric HIV-1 protease include high selectivity, potency, stability, and bioavailability. Pseudo-C2-symmetric monools and C2-symmetric diols, containing central hydroxymethylene and (R,R)-dihydroxyethylene moieties flanked by a variety of hydrophobic P1/P1' side chains, were studied as HIV-1 protease inhibitors. The monools and diols were synthesized in 8-10 steps from D-(+)-arabitol and D-(+)-mannitol, respectively. Monools with ethyl or isobutyl P1/P1' side chains were weak inhibitors of recombinant HIV-1 protease (Ki > 10 microM), while benzyl P1/P1' side chains afforded a moderately potent inhibitor (apparent Ki = 230 nM). Diols were 100-10,000x more potent than analogous monools, and a wider range of P1/P1' side chains led to potent inhibition. Both classes of compounds exhibited lower apparent Ki values under high-salt conditions. Surprisingly, monool and diol HIV-1 protease inhibitors were potent inhibitors of porcine pepsin, a prototypical asymmetric monomeric aspartic protease. These results were evaluated in the context of the pseudosymmetric structure of monomeric aspartic proteases and their evolutionary kinship with the retroviral proteases. The X-ray crystal structure of HIV-1 protease complexed with a symmetric diol was determined at 2.6 A. Contrary to expectations, the diol binds the protease asymmetrically and exhibits 2-fold disorder in the electron density map. Molecular dynamics simulations were conducted beginning with asymmetric and symmetric HIV-1 protease/inhibitor model complexes. A more stable trajectory resulted from the asymmetric complex, in agreement with the observed asymmetric binding mode. A simple four-point model was used to argue more generally that van der Waals and electrostatic force fields can commonly lead to an asymmetric association between symmetric molecules.

Quantitative structure-biodegradability relationships (QSBRs) using modified autocorrelation method (MAM)

Quantitative structure-biodegradability relationships (QSBRs) were established for a set of various organic compounds using autocorrelation components as molecular descriptors. The molecules were described by their size (van der Waals volume), electronegativity, hydrogen bonding donor and acceptor ability and lipophilicity (log P). In addition to the established models for alcohols, ketones, and aromatics, we have elaborated a model for both alcohols and ketones (5-day BOD = 0.06 V0 + 1.067 log P - 0.356 (log P)2; n = 29, r = 0.958, s = 0.44, F = 145.6) and another for all the compounds (5-day BOD = 0.065 V0 + 0.748 log P - 0.316 (log P)2; n = 43, r = 0.906, s = 0.575, F = 91.2).

Microsomal formation of a pyrrolic alcohol glutathione conjugate of the pyrrolizidine alkaloid senecionine

1. Pyrrolizidine alkaloids (PAs) are metabolized primarily to putative dehydroalkaloid (PA pyrrole) metabolites and to PA N-oxide by rat liver microsomal monooxygenases. 2. The dehydroalkaloids are highly reactive and either bind covalentely to tissue nucleophiles or are hydrolysed to the more stable pyrrole, (R,S)-6,7-dihydro-7-hydroxy-1-hydroxymethyl-5H-pyrrolizine (DHP), and the corresponding necic acid. 3. Addition of glutathione (GSH 1 mM) to incubation mixtures containing rat liver microsomes and the PA senecionine (SN), resulted in the formation of a conjugate of DHP with GSH. 5. The mass spectrum of this DHP-GSH conjugate was identical to that of the chemically-synthesized dehydroretronecine (the R enantiomer of the racemic DHP) and GSH. 6. Only negligible amounts of DHP-GSH conjugate were formed when DHP itself was incubated with GSH at physiological pH. 7. These findings provide strong evidence for the microsomal conversion of SN to a highly reactive metabolite, presumably dehydrosenecionine, which then reacts with GSH to form the DHP-GSH conjugate. 8. It is likely that a similar mechanism is responsible in vivo for the formation of GSH conjugates of DHP from SN and other PAs.

Mouse hepatic microsomal oxidation of aliphatic aldehydes (C8 to C11) to carboxylic acids

Addition of saturated and alpha, beta-unsaturated aliphatic aldehydes (C8 to C11) significantly increased NADPH oxidation with mouse hepatic microsomes, and the aldehydes themselves were oxidized to the corresponding carboxylic acids. When these aldehyde substrates were incubated similarly under oxygen-18 gas and the carboxylic acids formed were analyzed by GC-MS after methylation, it was indicated that oxygen-18 was significantly incorporated into the carboxylic acids formed from alpha, beta-unsaturated aldehydes, but not significantly into the carboxylic acids formed from saturated aldehydes. These results indicate that enzyme and/or mechanism responsible for the oxidation of these two types of aldehydes is different from each other.

Structural determinants for alcohol substrates to be oxidized to formaldehyde by rat liver microsomes

Glycerol can be oxidized to formaldehyde by rat liver microsomes and by cytochrome P450. The ability of other alcohols to be oxidized to formaldehyde was determined to evaluate the structural determinants of the alcohol which eventually lead to this production of formaldehyde. Monohydroxylated alcohols such as 1- or 2-propanol did not produce formaldehyde when incubated with NADPH and microsomes. Geminal diols such as 1,3-propanediol, 1,3-butanediol, or 1,4-butanediol also did not yield formaldehyde. However, vicinal diols such as 1,2-propanediol or 1,2-butanediol produced formaldehyde. With 1,2-propanediol, the residual two-carbon fragment was found to be acetaldehyde, while with 1,2-butanediol, the residual three-carbon fragment was propionaldehyde. Oxidation of 1,2-propanediol to formaldehyde plus acetaldehyde involved interaction with an oxidant derived from H2O2 plus nonheme iron, since production of the two aldehydic products was completely prevented by catalase or glutathione plus glutathione peroxidase and by chelators such as desferrioxamine or EDTA. The oxidant was not superoxide or hydroxyl radical. Product formation was fivefold lower when NADH replaced NADPH, and was inhibited by substrates, ligands, and inhibitors of cytochrome P450. A charged glycol such as alpha-glycerophosphate (but not the geminal beta-glycerophosphate) was readily oxidized to formaldehyde, suggesting that interaction of the glycol with the oxidant was occurring in solution and not in a hydrophobic environment. These results indicate that the carbon-carbon bond between 1,2-glycols can be cleaved by an oxidant derived from microsomal generated H2O2 and reduction of non-heme iron, with the subsequent production of formaldehyde plus an aldehyde with one less carbon than the initial glycol substrate.

Re-examination of the metabolic potentials of the acetogens Clostridium aceticum and Clostridium formicoaceticum: chemolithoautotrophic and aromatic-dependent growth

Both Clostridium formicoaceticum and Clostridium aceticum grew chemolithoautotrophically on carbon monoxide plus CO2 in defined medium in the absence of carbohydrates, amino acids, or other carbon and energy sources. Formate supported the growth of both organisms as well in both defined and undefined media (both of which also contained CO2). Hydrogen was stimulatory to the growth of C. formicoaceticum upon first transfer into H2-enriched formate medium; however, neither chemolithoautotrophic growth at the expense of H2 plus CO2 nor hydrogenase could be demonstrated with this acetogen. Consistent with recent findings with other acetogens, numerous aromatic compounds were utilized by C. aceticum and C. formicoaceticum: (i) aromatic methoxyl groups were O-demethylated; (ii) aromatic acrylates were reduced; and (iii) aromatic aldehydes were oxidized. These findings demonstrate that the metabolic potentials of these two acetogens are greater than previously recognized.

Physical and genetic mapping of the catA region of Pseudomonas aeruginosa

A prime plasmid has been used as the basis for the construction of a physical and genetic map of a 125 kb segment of the Pseudomonas aeruginosa PAO chromosome. Using pMO1811, a prime plasmid selected for the catA region, a series of Tn5 insertions were obtained which identified two new markers gcu (glycine utilization) and oap (organic acids and alcohols permeability) in the 125 kb region and located them in relation to other known markers of this region. A cosmid bank was constructed from the prime plasmid and an ordered array of cosmid clones for this region identified by restriction endonuclease mapping with EcoRI, HindIII and KpnI, as well as complementation mapping and chromosome walking. By Southern hybridization analyses, it was confirmed that the chromosomal insert carried by pMO1811 was flanked by single, tandemly arranged copies of IS21 and the orientation of the insert on this prime was determined. This cosmid bank provides a resource for the further analysis of this region of the P. aeruginosa genome.

Purification and characterisation of an NAD(+)-dependent secondary alcohol dehydrogenase from Pseudomonas maltophilia MB11L

A constitutive NAD(+)-linked alcohol dehydrogenase was purified 338-fold from cells of Pseudomonas maltophilia MB11L grown on glucose. Maximum activity was observed with cyclic and linear secondary alcohols, with little activity seen against primary or aromatic alcohols. Substrate oxidation activity was maximal at pH 10.0, while substrate reduction was optimal at pH 4.5. The Km values for propan-2-ol, NAD+ and acetone were 87, 413 and 143 microM respectively. The enzyme is a tetramer with subunit Mr of approximately 44,000. It has an isoelectric point of 4.75, and was inhibited by chelating agents, thiol reagents and certain metal ions.

Modification of bactericidal fatty acids by an enzyme of Staphylococcus aureus

Certain strains of Staphylococcus aureus produce an enzyme capable of inactivating the bactericidal fatty acids produced in staphylococcal abscesses by esterification to various alcohols. The enzyme, called FAME (fatty acid modifying enzyme), has a pH optimum between 5.5 and 6.0 and a temperature optimum of about 40 degrees C. Enzyme activity is not affected by edetic acid or by the presence or absence of sodium and potassium ions. Although FAME can utilise methanol, ethanol, 1-propanol, 2-propanol, 1-butanol or cholesterol as substrates, cholesterol appears to be the preferred substrate. FAME esterifies without being an esterase operating in reverse. Strains capable of producing the enzyme can synthesise it in trypticase soy broth and in a chemically defined medium, but not necessarily in equal amounts. FAME production is correlated with the ability of a strain to grow and survive within the tissues.

Human alcohol dehydrogenase: dependence of secondary alcohol oxidation on the amino acids at positions 93 and 94

The human liver alpha alpha and beta 1 beta 1 isoenzymes are straight-chain alcohol dehydrogenases with different efficiencies toward secondary alcohols. Two of the 24 amino acid substitutions in alpha alpha (A for F93 and I for T94) were made by site-directed mutagenesis of beta 1 beta 1 and the substrate specificity of beta 93A94I was examined. The Vmax/KM values of beta 93A94I for secondary alcohols (especially R enantiomers) are similar to that of alpha alpha and as much as 4000-fold greater than beta 1 beta 1, but the dependences of Vmax/KM on primary alcohol chain length are similar to beta 1 beta 1, but not alpha alpha. Thus, the substitutions of A for F93 and I for T94 in beta 1 beta 1 account for the increased efficiency towards secondary alcohols and stereoselectivity for enantiomeric alcohols, but not for the effects of chain length on the Vmax/KM for primary alcohols seen with alpha alpha.