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PubMed1987

Isolated tumoral pyruvate dehydrogenase can synthesize acetoin which inhibits pyruvate oxidation as well as other aldehydes.

Oxidation of 1 mM pyruvate by Ehrlich and AS30-D tumor mitochondria is inhibited by acetoin, an unusual and important metabolite of pyruvate utilization by cancer cells, by acetaldehyde, methylglyoxal and excess pyruvate. The respiratory inhibition is reversed by other substrates added to pyruvate and also by 0.5 mM ATP. Kinetic properties of pyruvate dehydrogenase complex isolated from these tumor mitochondria have been studied. This complex appears to be able to synthesize acetoin from acetaldehyde plus pyruvate and is competitively inhibited by acetoin. The role of a new regulatory pattern for tumoral pyruvate dehydrogenase is presented.

Acetoin↗

PubMed1993

Catalysis of acetoin formation by brewers' yeast pyruvate decarboxylase isozymes.

Catalysis of C(alpha)-proton transfer from 2-(1-hydroxyethyl)thiamin diphosphate (HETDP) by pyruvate decarboxylase isozymes (PDC; EC 4.1.1.1) from Saccharomyces carlsbergensis was investigated by determining the steady-state kinetics of the reaction of [1-L]acetaldehyde (L = H, D, or T) to form acetoin and the primary kinetic isotope effects on the reaction. The PDC isozyme mixture and alpha 4 isozyme (alpha 4-PDC) have different steady-state kinetic parameters and isotope effects for acetoin formation in the presence and absence of the nonsubstrate allosteric effector pyruvamide: pyruvamide activation occurs by stabilization of the acetaldehyde/PDC ternary complex. The magnitudes of primary L(V/K)-type (L = D or T) isotope effects on C(alpha)-proton transfer from alpha 4-PDC-bound HETDP provide no evidence for significant breakdown of the Swain-Schaad relationship that would indicate partitioning of the putative C(alpha)-carbanion/enamine intermediate between HETDP and products. The substrate concentration dependence of the deuterium primary kinetic isotope effects provides evidence for an intrinsic isotope effect of 4.1 for C(alpha)-proton transfer from alpha 4-PDC-bound HETDP. A 1.10 +/- 0.02-fold 14C isotope discrimination against [1,2-14C]acetaldehyde in acetoin formation is inconsistent with a stepwise mechanism, in which the addition step occurs after rate-limiting formation of the C(alpha)-carbanion/enamine as a discrete enzyme-bound intermediate, and provides evidence for a concerted reaction mechanism with an important component of carbon-carbon bond formation in the transition state.

Acetaldehyde↗

PubMed1995

Production of high levels of acetoin in Saccharomyces cerevisiae wine yeasts is a recessive trait.

A genetic study of acetoin production was performed on wild wine yeast strains of Saccharomyces cerevisiae producing different amounts of the compound. By using differences found in these strains as source of genetic variability, it was found that crosses between high and low acetoin producing strains yielded the low level in the hybrids, indicating the low production as a dominant trait. Tetrad analysis showed that high vs low acetoin production is segregated as a single gene.

Acetoin↗

PubMed1976

Studies on the formation of acetoin from acetaldehyde by the pyruvate dehydrogenase complex and its regulation.

1. Pyruvate dehydrogenase complex was isolated from pigeon breast muscle involving steps of isoelectric precipitation, poly(ethyleneglycol) fractionation and separation on a glycerine gradient in the ultracentrifuge. 2. Arsenite, a potent inhibitor of the dihydrolipoyl transcetylase, did not affect the formation of acetoin from acetaldehyde, indicating that the pyruvate dehydrogenase component was operative in this reaction. 3. Production of acetoin by the pyruvate dehydrogenase complex is subject to regulation by phosphorylation and dephosphorylation, the dephosphorylated form only being active. 4. The inhibition by acetaldehyde of the pyruvate dehydrogenase complex could be partly explained by the formation of acetoin as an alternative reaction.

Acetaldehyde↗

PubMed1996

Determination of 2,3-butanediol in high and low acetoin producers of Saccharomyces cerevisiae wine yeasts by automated multiple development (AMD).

High performance thin layer chromatography with automated multiple development was used to determine 2,3-butanediol levels in wine produced by high and low acetoin-forming strains of Saccharomyces cerevisiae. An inverse correlation between acetoin and 2,3-butanediol content was found suggesting a leaky mutation in acetoin reductase of the low 2,3-butanediol producing strains.

Acetoin↗

PubMed1991

Identification and molecular characterization of the Alcaligenes eutrophus H16 aco operon genes involved in acetoin catabolism.

Acetoin:dichlorophenolindophenol oxidoreductase (Ao:DCPIP OR) and the fast-migrating protein (FMP) were purified to homogeneity from crude extracts of acetoin-grown cells of Alcaligenes eutrophus. Ao:DCPIP OR consisted of alpha and beta subunits (Mrs, 35,500 and 36,000, respectively), and a tetrameric alpha 2 beta 2 structure was most likely for the native protein. The molecular weight of FMP subunits was 39,000. The N-terminal amino acid sequences of the three proteins were determined, and oligonucleotides were synthesized on the basis of the codon usage of A. eutrophus. With these, the structural genes for the alpha and beta subunits of Ao:DCPIP OR and FMP, which were referred to as acoA, acoB, and acoC, respectively, were localized on one single EcoRI restriction fragment which has been cloned recently (C. Fründ, H. Priefert, A. Steinbüchel, and H. G. Schlegel, J. Bacteriol. 171:6539-6548, 1989). The nucleotide sequences of a 5.3-kbp region of this fragment and one adjacent fragment were determined, and the structural genes for acoA (1,002 bp), acoB (1,017 bp), and acoC (1,125 bp) were identified. Together with the gene acoX, whose function is still unknown and which is represented by a 1,080-bp open reading frame, these genes are probably organized in one single operon (acoXABC). The transcription start site was identified 27 bp upstream of acoX; this site was preceded by a region which exhibited complete homology to the enterobacterial sigma 54-dependent promoter consensus sequence. The amino acid sequences deduced from acoA and acoB for the alpha subunit (Mr, 35,243) and the beta subunit (Mr, 35,788) exhibited significant homologies to the primary structures of the dehydrogenase components of various 2-oxo acid dehydrogenase complexes, whereas those deduced from acoC for FMP (Mr, 38,941) revealed homology to the dihydrolipoamide acetyltransferase of Escherichia coli. The occurrence of a new enzyme type for the degradation of acetoin is discussed.

Acetoin↗

PubMed1992

Identification of acoR, a regulatory gene for the expression of genes essential for acetoin catabolism in Alcaligenes eutrophus H16.

Two hundred thirty-nine base pairs upstream from acoXABC, which encodes the Alcaligenes eutrophus H16 structural genes essential for cleavage of acetoin, the 2,004-bp acoR gene was identified. acoR encodes a protein of 668 amino acids with a molecular mass of 72.9 kDa. The amino acid sequence deduced from acoR exhibited homologies to the primary structures of transcriptional activators such as NifA of Azotobacter vinelandii, NtrC of Klebsiella pneumoniae, and HoxA of A. eutrophus. Striking similarities to the central domain of these proteins and the presence of a typical nucleotide-binding site (GETGSGK) as well as of a C-terminal helix-turn-helix motif as a DNA-binding site were revealed. Between acoR and acoXABC, two different types of sequences with dual rotational symmetry [CAC-(N11 to N18)-GTG and TGT-(N10 to N14)-ACA] were found; these sequences are similar to NtrC and NifA upstream activator sequences, respectively. Determination of the N-terminal amino acid sequence of an acoR'-'lacZ gene fusion identified the translational start of acoR. S1 nuclease protection assay identified the transcriptional start site 109 bp upstream of acoR. The promoter region (TTGCGC-N18-TACATT) resembled the sigma 70 consensus sequence of Escherichia coli. Analysis of an acoR'-'lacZ fusion and primer extension studies revealed that acoR was expressed at a low level under all culture conditions, whereas acoXABC was expressed only in acetoin-grown cells. The insertions of Tn5 in six transposon-induced acetoin-negative mutants of A. eutrophus were mapped within acoR. On the basis of these studies, it is probable that AcoR represents a regulatory protein which is required for sigma 54-dependent transcription of acoXABC.

Acetoin↗

PubMed1961

Role of citritase in acetoin formation by Streptococcus diacetilactis and Leuconostoc citrovorum.

Harvey, R. J. (University of California, Davis) and E. B. Collins. Role of citritase in acetoin formation by Streptococcus diacetilactis and Leuconostoc citrovorum. J. Bacteriol. 82:954-959. 1961.-Cell-free extracts of Streptococcus diacetilactis and Leuconostoc citrovorum converted citrate to acetate, oxalacetate, pyruvate, carbon dioxide, and acetoin. The products, stoichiometry, and cofactor requirements of the citrate-splitting reaction were identical to those reported for citritase. Coenzyme A was not required; the reaction was stimulated by magnesium or manganous ions, and inhibited by calcium ions. In S. diacetilactis the enzyme is constitutive; it has been found inducible in all other organisms that have been studied. Ten strains of S. diacetilactis, three strains of Leuconostoc, and one strain of S. liquefaciens contained the enzyme; 21 strains of S. cremoris and 3 strains of S. lactis did not. Cell-free extracts of S. diacetilactis and L. citrovorum converted pyruvate to acetoin and carbon dioxide in the presence of manganous ions and thiamine pyrophosphate.

Acetates↗

PubMed2005

Method for the simultaneous assay of diacetyl and acetoin in the presence of alpha-acetolactate: application in determining the kinetic parameters for the decomposition of alpha-acetolactate.

A simultaneous assay method for diacetyl and acetoin was developed to investigate the formation of diacetyl during the brewing of alcoholic beverages. A GC-MS analysis after the extraction from neutralized sample by ethyl acetate gave accurate assay results. The detection limit was below 0.1 mg/l and the assay was quantitative from 0.1 to 100 mg/l for both compounds. Unlike other methods, the assay results were unaffected by the presence of alpha-acetolactate (up to 26 mg/l), which easily decomposes to diacetyl or acetoin, because the extraction condition prevents the decomposition and extraction of this acidic compound. Since our assay is compatible with samples that contain alpha-acetolactate, the kinetic parameters for decomposition of alpha-acetolactate to diacetyl and acetoin were determined. The decomposition rate constants were affected by the ethanol concentration. Overall kinetics for the decomposition of alpha-acetolactate was formulated as a function of ethanol concentration, pH and temperature. The kinetics can be applied to alcoholic beverages such as sake.

Acetoin↗

PubMed1987

Oversynthesis of diacetyl and acetoin in a riboflavin deficient mutant of yeast.

The relations of diacetyl and acetoin to flavinogenesis were studied using a variety of the riboflavin deficient mutants of yeast. The results obtained indicated that only the mutant N189-10A, which have a defect in the pathway positioned next to the nucleotide precursor, guanosine triphosphate (GTP), produces prodigeous amounts of diacetyl and acetoin among the mutants and the wild strain used. A close relation of diacetyl and acetoin to riboflavin formation at their substrate level or regulator level was discussed.

Acetoin↗

PubMed1987

Detection of acetoin by head-space gas-liquid chromatography for rapid identification of bacteremia caused by Klebsielleae.

Head-space gas-liquid chromatographic (HS-GLC) detection of acetoin in 223 blood cultures of gram-negative bacilli was compared with results obtained from the conventional identification method. Seventy-three out of 76 cultures of Klebsielleae, including Klebsiella pneumoniae, Klebsiella oxtytoca, Enterobacter cloacae, Enterobacter agglomerans and Serratia marcescens, were identified by the acetoin detection method with HS-GLC. One hundred and forty-six out of 147 blood cultures of other gram-negative aerobic and anaerobic bacilli did not produce acetoin. The findings indicate that the HS-GLC technique is a useful method with high sensitivity and specificity for identification of bacteremia caused by Klebsielleae.

Acetoin↗

PubMedDate not supplied

[Relation of acetoin and valine in Enterobacteriaceae cultures on media with glucose and glycerin].

The ratio between acetoin and valine produced by the cultures of the family Enterobacteriaceae changes upon the addition of glucose and glycerol or their mixture to a defined medium. The experiments were carried out with 12 strains of Aerobacter aerogenes and 2 strains of Aerobacter cloacae and Serratia marcescens. The highest yield of acetoin was found on the medium with glucose (12.5--13.0 g/litre); the maximum accumulation of valine was registered on the medium with glucose and glycerol (1.8--4.8 g/litre). The presence of glycerol in the medium decreased the production of acetoin by 27--85 percent compared to that on the glucose-mineral medium.

Acetoin↗

PubMed1987

High-Efficiency Conversion of Pyruvate to Acetoin by Lactobacillus plantarum during pH-Controlled and Fed-Batch Fermentations.

The influence of pH on the type and concentration of metabolites produced from pyruvate by Lactobacillus plantarum ATCC 8014 was examined in pH-controlled fermentors at pH values of 4.5 to 6.5. Specific growth rates, cell dry weights, and diacetyl concentrations were highest at pH 5.5, with values of 0.78 h, 190 mg/liter, and 1.2 mM, respectively. While the conversion efficiency (millimoles of acetoin formed per millimoles of pyruvate utilized) was highest (94.6%) at pH 4.5, acetoin levels were similar (20 mM) between pH 4.5 and 5.5. Feeding stationary-phase cells exogenous pyruvate increased acetoin levels to 78 mM.

Journal Article↗

PubMed1990

Acetoin Fermentation by Citrate-Positive Lactococcus lactis subsp. lactis 3022 Grown Aerobically in the Presence of Hemin or Cu.

CitrLactococcus lactis subsp. lactis 3022 produced more biomass and converted most of the glucose substrate to diacetyl and acetoin when grown aerobically with hemin and Cu. The activity of diacetyl synthase was greatly stimulated by the addition of hemin or Cu, and the activity of NAD-dependent diacetyl reductase was very high. Hemin did not affect the activities of NADH oxidase and lactate dehydrogenase. These results indicated that the pyruvate formed via glycolysis would be rapidly converted to diacetyl and that the diacetyl would then be converted to acetoin by the NAD-dependent diacetyl reductase to reoxidize NADH when the cells were grown aerobically with hemin or Cu. On the other hand, the Y(Glu) value for the hemincontaining culture was lower than for the culture without hemin, because acetate production was repressed when an excess of glucose was present. However, in the presence of lipoic acid, an essential cofactor of the dihydrolipoamide acetyltransferase part of the pyruvate dehydrogenase complex, hemin or Cu enhanced acetate production and then repressed diacetyl and acetoin production. The activity of diacetyl synthase was lowered by the addition of lipoic acid. These results indicate that hemin or Cu stimulates acetyl coenzyme A (acetyl-CoA) formation from pyruvate and that lipoic acid inhibits the condensation of acetyl-CoA with hydroxyethylthiamine PP(i). In addition, it appears that acetyl-CoA not used for diacetyl synthesis is converted to acetate.

Journal Article↗

PubMed1997

Diacetyl and acetoin production from the co-metabolism of citrate and xylose by Leuconostoc mesenteroides subsp. mesenteroides.

The co-metabolism of citrate plus xylose by Leuconostoc mesenteroides subsp. mesenteroides results in a growth stimulation, an increase in D-lactate and acetate production and repression of ethanol production. This correlated well with the levels of key enzymes involved. A partial repression of alcohol dehydrogenase and a marked stimulation of acetate kinase were observed. High citrate bioconversion yields in diacetyl plus acetoin were obtained at pH 5.2 in batch (11.5%) or in chemostat (up to 17.4%) culture. In contrast, no diacetyl or acetoin was detected in citrate plus glucose fermentation.

Acetoin↗

PubMed2004

Enhanced production of acetoin and butanediol in recombinant Enterobacter aerogenes carrying Vitreoscilla hemoglobin gene.

Microbial production of butanediol and acetoin has received increasing interest because of their diverse potential practical uses. Although both products are fermentative in nature, their optimal production requires a low level of oxygen. In this study, the use of a recombinant oxygen uptake system on production of these metabolites was investigated. Enterobacter aerogenes was transformed with a pUC8-based plasmid carrying the gene (vgb) encoding Vitreoscilla (bacterial)hemoglobin (VHb). The presence of vgb and production of VHb by this strain resulted in an increase in viability from 72 to 96 h in culture, but no overall increase in cell mass. Accumulation of the fermentation products acetoin and butanediol were enhanced (up to 83%) by the presence of vgb/VHb. This vgb/VHb related effect appears to be due to an increase of flux through the acetoin/butanediol pathway, but not at the expense of acid production.

Acetoin↗

PubMed1989

Urinary excretion of 2,3-butanediol and acetoin by babies on a special care unit.

2,3-Butanediol was detected by capillary gas chromatography in 45 urine samples from 20 babies on a special care unit, 17 of whom were premature. The meso form of the diol predominated and in 21 samples was the only diastereoisomer present. Acetoin was found in 20 of the samples. It was never detected in the absence of 2,3-butanediol. 2,3-Butanediol was not detectable in more than trace amounts in urine from 66 other babies on the unit. The most likely origin of these compounds was from bacterial fermentation of pyruvate in the gut. Their presence may be explained by abnormal gut colonisation with acetoin-producing microorganisms, an abundant supply of nutrient lactose in the colon and increased intestinal permeability. It is further evidence of the magnitude of intestinal carbohydrate fermentation in preterm babies. 2,3-Butanediol could prove a useful biochemical marker for abnormal colonisation of neonates on special care units.

Acetoin↗

PubMed2003

The species-specific ratios of 2,3-butanediol and acetoin isomers as a tool to evaluate wine yeast performance.

The isomers of 2,3-butanediol [R,R; S,S; R,S (meso-form)] and of acetoin (R,S) were determined in laboratory wine fermentations carried out by 50 yeast strains, 10 for each of the following species, Saccharomyces cerevisiae, Kloeckera apiculata, Candida stellata, Metschnikowia pulcherrima and Brettanomyces bruxellensis, in order to evaluate if such parameters might be used to differentiate wines obtained with different yeast species. According to analysis of variance (ANOVA), the strains of the same species behaved similarly, whereas the five yeast species behaved differently so that species-specific profiles were recognized. Moreover, the discriminant analysis grouped the wines into five groups, each including the 10 wines obtained by the 10 yeast strains of the same species. Trials were also included where musts partially fermented by non-Saccharomyces species were inoculated with a selected strain of S. cerevisiae to complete fermentation, and the content in 2,3-butanediol and acetoin isomers was again determined and statistical analysis was performed. Although the final values of these parameters resembled those obtained in pure fermentation with S. cerevisiae, statistical analysis discriminated wines according to the yeast species performing the first fermentation phase.

Acetoin↗