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PubMed1993

Acetoin production in Saccharomyces cerevisiae wine yeasts.

One hundred strains of Saccharomyces cerevisiae were examined for the capacity to produce acetoin in synthetic medium and in grape must. The low production of acetoin was found to be the more common pattern in this species. Most strains exhibited a similar distribution in both media, production ranging from non-detectable amounts to 12 mg l-1. Only four strains produced high quantities of acetoin, up to 29.5 mg l-1 in synthetic medium and up to 194.6 mg l-1 in grape must. This biometric study showed the existence of two phenotypes, "low and high acetoin production", that could be selected for conferring a desirable flavour of the final product.

Acetoin↗

PubMed1984

Brewers' yeast pyruvate decarboxylase produces acetoin from acetaldehyde: a novel tool to study the mechanism of steps subsequent to carbon dioxide loss.

A gas-liquid chromatographic technique was developed for the determination of both acetaldehyde and the 3-4% acetoin side product that results from the brewers' yeast pyruvate decarboxylase (EC 4.1.1.1) catalyzed reaction of pyruvic acid. Employing this method enabled the demonstration of the catalysis of acetaldehyde condensation to acetoin by the enzyme. It was found that the acetoin produced enzymatically from pyruvic acid or from acetaldehyde was optically active, thus providing stereochemical information about the reaction. Deuterium kinetic isotope effects (employing CH3CHO and CH3CDO) were determined on the steady-state kinetic parameters to be 4.5 (Vmax) and 3.2 (Vmax/Kappm), respectively. This enabled, for the first time, the estimation of relative kinetic barriers for steps past decarboxylation. It could be concluded that (a) C-H bond scission was part of rate limitation in the enzyme-catalyzed condensation of acetaldehyde to acetoin and that (b) among the steps leading to the release of acetaldehyde, protonation of the key enamine intermediate was part of rate limitation. This latter finding is also directly applicable to the mechanism of pyruvate decarboxylation.

Acetaldehyde↗

PubMed2003

(R)-acetoin-female sex pheromone of the summer chafer Amphimallon solstitiale (L.).

Extracts of Amphimallon solstitiale (L.), a well known, widely distributed and rather common European scarab beetle, were analyzed by GC-MS and GC-EAD. Acetoin - (R):(S) > 9:1 - as well as 2,3-butanediol - (2R,3R): (2S,3S):meso = 1:1:9 - were present in extracts of both males and females. Although (2S,3S)-butanediol did not show any EAD activity, the other compounds elicited strong responses exclusively with male antennae. In contrast, several EAD active green leaf volatiles were detected equally well by male and female antennae. During preliminary field bioassays, (R)-acetoin was highly attractive to swarming males, whereas neither rac-acetoin nor the 2,3-butanediols showed activity. Therefore, (R)-acetoin is the female sex pheromone of A. solstitiale.

Acetoin↗

PubMed2000

Mutagenesis at asp27 of pyruvate decarboxylase from Zymomonas mobilis. Effect on its ability to form acetoin and acetolactate.

Pyruvate decarboxylase (PDC) is one of several enzymes that require thiamin diphosphate (ThDP) and a bivalent cation as essential cofactors. The three-dimensional structure of PDC from Zymomonas mobilis (ZMPDC) shows that Asp27 (D27) is close to ThDP in the active site, and mutagenesis of this residue has suggested that it participates in catalysis. The normal product of the PDC reaction is acetaldehyde but it is known that the enzyme can also form acetoin as a by-product from the hydroxyethyl-ThDP reaction intermediate. This study focuses on the role of D27 in the production of acetoin and a second by-product, acetolactate. D27 in ZMPDC was altered to alanine (D27A) and this mutated protein, the wild-type, and two other previously constructed PDC mutants (D27E and D27N) were expressed and purified. Determination of the kinetic properties of D27A showed that the affinity of D27A for ThDP is decreased 30-fold, while the affinity for Mg2+ and the Michaelis constant for pyruvate were similar to those of the wild-type. The time-courses of their reactions were investigated. Each mutant has greatly reduced ability to produce acetaldehyde and acetoin compared with the wild-type PDC. However, the effect of these mutations on acetaldehyde production is greater than that on acetoin formation. The D27A mutant can also form acetolactate, whereas neither of the other mutants, nor the wild-type PDC, can do so. In addition, acetaldehyde formation and/or release are reversible in wild-type ZMPDC but irreversible for the mutants. The results are explained by a mechanism involving thermodynamic and geometric characteristics of the intermediates in the reaction.

Acetaldehyde↗

PubMed1997

Isolation and properties of Lactococcus lactis subsp. lactis biovar diacetylactis CNRZ 483 mutants producing diacetyl and acetoin from glucose.

Following treatment with the mutagen N-methyl-N'-nitro-N-nitrosoguanidine, three mutants of Lactococcus lactis subsp. lactis biovar diacetylactis CNRZ 483 that produced diacetyl and acetoin from glucose were isolated. The lactate dehydrogenase activity of these mutants was strongly attenuated, and the mutants produced less lactate than the parental strain. The kinetic properties of lactate dehydrogenase of strain CNRZ 483 and the mutants revealed differences in the affinity of the enzyme for pyruvate, NADH, and fructose-1,6-diphosphate. When cultured aerobically, strain CNRZ 483 transformed 2.3% of glucose to acetoin and produced no diacetyl or 2,3-butanediol. Under the same conditions, mutants 483L1, 483L2, and 483L3 transformed 42.0, 78.9, and 75.8%, respectively, of glucose to C4 compounds (diacetyl, acetoin, and 2,3-butanediol). Anaerobically, strain CNRZ 483 produced no C4 compounds, while mutants 483L1, 483L2, and 483L3 transformed 2.0, 37.0, and 25.8% of glucose to acetoin and 2,3-butanediol. In contrast to the parental strain, the NADH balance showed that the mutants regenerated most of the NAD via NADH oxidase under aerobic conditions and by ethanol production under anaerobic conditions.

Acetoin↗

PubMed2003

Plasmid-encoded diacetyl (acetoin) reductase in Leuconostoc pseudomesenteroides.

A plasmid-borne diacetyl (acetoin) reductase (butA) from Leuconostoc pseudomesenteroides CHCC2114 was sequenced and cloned. Nucleotide sequence analysis revealed an open reading frame encoding a protein of 257 amino acids which had high identity at the amino acid level to diacetyl (acetoin) reductases reported previously. Downstream of the butA gene of L. pseudomesenteroides, but coding in the opposite orientation, a putative DNA recombinase was identified. A two-step PCR approach was used to construct FPR02, a butA mutant of the wild-type strain, CHCC2114. FPR02 had significantly reduced diacetyl (acetoin) reductase activity with NADH as coenzyme, but not with NADPH as coenzyme, suggesting the presence of another diacetyl (acetoin)-reducing activity in L. pseudomesenteroides. Plasmid-curing experiments demonstrated that the butA gene is carried on a 20-kb plasmid in L. pseudomesenteroides.

Acetoin Dehydrogenase↗

PubMed1994

Acetoin catabolic system of Klebsiella pneumoniae CG43: sequence, expression, and organization of the aco operon.

A cosmid clone which was capable of depleting acetoin in vivo was isolated from a library of Klebsiella pneumoniae CG43 cosmids. The smallest functional subclone contained a 3.9-kb DNA fragment of the cosmid clone. Sequencing of the DNA fragment revealed three open reading frames (ORFs A, B, and C) encoding polypeptides of 34, 36, and 52 kDa, respectively. The presence of these proteins was demonstrated by expression of the recombinant DNA clone in Escherichia coli. Considerable similarities between the deduced amino acid sequences of the ORFs and those of the following enzymes were found: acetoin dissimilation enzymes, pyruvate dehydrogenase complex, 2-oxoglutarate dehydrogenase complex, and branched-chain 2-oxo acid dehydrogenase complex of various origins. Activities of these enzymes, including acetoin-dependent dichlorophenolin-dohenol oxidoreductase and dihydrolipoamide acetyltransferase, were detected in the extracts of E. coli harboring the genes encoding products of the three ORFs. Although not required for acetoin depletion in vivo, a possible fourth ORF (ORF D), located 39 nucleotides downstream of ORF C, was also identified. The deduced N-terminal sequence of the ORF D product was highly homologous to the dihydrolipoamide dehydrogenases of several organisms. Primer extension analysis identified the transcriptional start of the operon as an A residue 72 nucleotides upstream of ORF A.

3-Methyl-2-Oxobutanoate Dehydrogenase (Lipoamide)↗

PubMed2000

An operon for a putative ATP-binding cassette transport system involved in acetoin utilization of Bacillus subtilis.

The ytrABCDEF operon of Bacillus subtilis was deduced to encode a putative ATP-binding cassette (ABC) transport system. YtrB and YtrE could be the ABC subunits, and YtrC and YtrD are highly hydrophobic and could form a channel through the cell membrane, while YtrF could be a periplasmic lipoprotein for substrate binding. Expression of the operon was examined in cells grown in a minimal medium. The results indicate that the expression was induced only early in the stationary phase. The six ytr genes form a single operon, transcribed from a putative sigma(A)-dependent promoter present upstream of ytrA. YtrA, which possesses a helix-turn-helix motif of the GntR family, acts probably as a repressor and regulates its own transcription. Inactivation of the operon led to a decrease in maximum cell yield and less-efficient sporulation, suggesting its involvement in the growth in stationary phase and sporulation. It is known that B. subtilis produces acetoin as an external carbon storage compound and then reuses it later during stationary phase and sporulation. When either the entire ytr operon or its last gene, ytrF, was inactivated, the production of acetoin was not affected, but the reuse of acetoin became less efficient. We suggest that the Ytr transport system plays a role in acetoin utilization during stationary phase and sporulation.

ATP-Binding Cassette Transporters↗

PubMed1963

ROLES OF CITRATE AND ACETOIN IN THE METABOLISM OF STREPTOCOCCUS DIACETILACTIS.

Harvey, R. J. (University of California, Davis), and E. B. Collins. Roles of citrate and acetoin in the metabolism of Streptococcus diacetilactis. J. Bacteriol. 86:1301-1307. 1963.-Streptococcus diacetilactis was unable to use citrate as a source of energy for growth, but the addition of citrate to a lactose-containing medium increased the specific growth rate 35%. Besides serving as the precursor of acetoin, some of the pyruvate formed from citrate was incorporated into cell material, primarily into lipids. A constant fraction of the weight of new cells was synthesized from the pyruvate formed from citrate. The rate of entry of citrate into cells was independent of the growth rate, and the usual result was that more pyruvate was formed from citrate than was required for cell synthesis. All excess pyruvate was converted to acetoin. Thus, acetoin formation acts as a detoxification mechanism, a means of removing intracellular pyruvate not required for synthesis of cell material.

Acetoin↗

PubMed1975

Analysis of acetoin and diacetyl in bacterial culture supernatants by gas-liquid chromatography.

The acetoin and diacetyl contents of culture supernatants of Voges-Proskauer-positive "viridans" streptotocci, Klebsiella pneumoniae and Staphylococcus aureus, were determined by a gas liquid chromatographic procedure, in which supernatants were extracted with diethyl ether and diacetyl was measured on columns of 10% (wt/wt) polyethylene glycol 400 (PEG 400) at 73 C. Acetoin was converted to diacetyl, before analysis, by a simple oxidation procedure with ferric chloride and without a distillation step. Streptococcal culture supernatants were shown by this method to contain only acetoin; supernatants of K. pneumoniae and S. aureus contained both acetoin and diacetyl.

Acetoin↗

PubMed1998

Effects of ethanol, acetoin and 2,3-butanediol on EEG power spectra in conscious rats.

Effects of ethanol, acetoin and 2,3-butanediol on the central nervous system (CNS) were investigated by using the analysis of EEG (electroencephalogram) spectral powers recorded at the frontal cortex in rats. High doses of ethanol were required for exhibiting an increase of EEG spectral powers in the delta (0-4 Hz) and theta (4-8 Hz) waves when it was given either orally or intravenously. On the other hand, when ethanol was injected intracerebroventricularly, the drug caused a potent increasing effect of EEG spectral powers. Both acetoin and 2,3-butanediol were found to increase in EEG spectral powers by oral and intravenous administrations at relatively low doses. In addition, acetoin and 2,3-butanediol were more effective than ethanol in increasing EEG spectral powers in the delta and theta bands after intracerebroventricular administration. From these findings it can be concluded that both acetoin and 2,3-butanediol have a potent CNS depressant effect.

Acetoin↗

PubMedDate not supplied

[Acetoin metabolism in animal tissues].

The acetoin-synthesizing activity has been studied in the skeletal muscles, brain, liver and spleen homogenates (numbered as the activity decreases). The acetoin-synthesizing activity drastically increases in case of the acetaldehyde excess and alcohol intoxication. The acetaldehyde concentrations of above 1.10(-3) M inhibit the liver pyruvate dehydrogenase activity and increase the non-oxidative transformation of pyruvate. Acetoin is rapidly metabolized in the organism eliminating from blood 10 minutes after its injection. Acetoin is an effective precursor in the biosynthesis of lipids.

Acetaldehyde↗

PubMed1987

Formation and utilization of acetoin, an unusual product of pyruvate metabolism by Ehrlich and AS30-D tumor mitochondria.

[14C]Pyruvate was rapidly non-oxidatively decarboxylated by Ehrlich tumor mitochondria at a rate of 40 nmol/min/mg of protein in the presence or absence of ADP. A search for decarboxylation products led to significant amounts of acetoin formed when Ehrlich tumor mitochondria were incubated with 1 mM [14C] pyruvate in the presence of ATP. Added acetoin to aerobic tumor mitochondria was rapidly utilized in the presence of ATP at a rate of 65 nmol/min/mg of protein. Citrate has been found as a product of acetoin utilization and was exported from the tumor mitochondria. Acetoin has been found in the ascitic liquid of Ehrlich and AS30-D tumor-bearing animals. These unusual reactions were not observed in control rat liver mitochondria.

Acetoin↗

PubMedDate not supplied

Isolation, purification, and study of certain properties of diacetyl(acetoin) reductase in the yeast Saccharomyces vini.

A highly active preparation of diacetyl(acetoin) reductase was isolated from cell-free extracts of the yeast Saccharomyces vini. Since the activity ratio of 2,3-butanediol dehydrogenase and diacetyl(acetoin) reductase was practically unchanged in the process of 65-fold purification, it can be assumed that the yeast cells contain one enzyme, which catalyzes both the reversible oxidation of 2,3-butanediol to acetoin by NAD and the practically irreversible reduction of diacetyl to acetoin by NAD-H2. Some properties of this enzyme were studied.

Acetoin Dehydrogenase↗

PubMed1996

Properties of diacetyl (acetoin) reductase from Bacillus stearothermophilus.

The cells of Bacillus stearothermophilus contain an NADH-dependent diacetyl (acetoin) reductase. The enzyme was easily purified to homogeneity, partially characterised, and found to be composed of two subunits with the same molecular weight. In the presence of NADH, it catalyses the stereospecific reduction of diacetyl first to (3S)-acetoin and then to (2S,3S)-butanediol; in the presence of NAD+, it catalyses the oxidation of (2S,3S)- and meso-butanediol, respectively, to (3S)-acetoin and to (3R)-acetoin, but is unable to oxidise these compounds to diacetyl. The enzyme is also able to catalyse redox reactions involving some endo-bicyclic octen- and heptenols and the related ketones, and its use is suggested also for the recycling of NAD+ and NADH in enzymatic redox reactions useful in organic syntheses.

Alcohol Oxidoreductases↗

PubMed1992

Conversion of Pyruvate to Acetoin Helps To Maintain pH Homeostasis in Lactobacillus plantarum.

Pyruvate is the substrate for diacetyl and acetoin synthesis by lactobacilli. Exogenous pyruvate stimulates acetoin production when glucose is present as an energy source. In Lactobacillus plantarum ATCC 8014, the energy derived from glucose via glycolysis generated a constant proton motive force of about -120 mV. At a low external pH, energized cells rapidly transported and accumulated pyruvate but did not do so when they were deenergized by nigericin. When large amounts of pyruvate were transported and subsequently accumulated internally, the cotransported protons rapidly lowered the internal pH. The conversion of pyruvate to acetoin instead of acidic end products contributed to the maintenance of pH homeostasis. This is the first report showing that the conversion of pyruvate to acetoin serves as a mechanism of pH homeostasis.

Journal Article↗

PubMed1978

Laboratory-scale production of acetoin plus diacetyl by Enterobacter cloacae ATCC 27613.

Conditions for the laboratory-scale production of acetoin plus diacetyl by Enterobacter cloacae ATCC 27613 were studied. Thirty-five g acetoin plus diacetyl/50 g sucrose were obtained when fermentation was carried out in 2.5 liter medium containing 12.5 g peptone and 12.5 g yeast extract, at pH 7.0, in a 5 liter conical flask on a shaker (240 rpm) at 28-30 degrees C for 48 hr. Recovery of pure diacetyl was 85% of the total acetoin plus diacetyl.

Acetoin↗

PubMed1990

Role of acetoin on the regulation of intermediate metabolism of Ehrlich ascites tumor mitochondria: its contribution to membrane cholesterol enrichment modifying passive proton permeability.

Acetoin, an unusual metabolite of highly glycolytic mammalian tumor cells, is synthesized from decarboxylated pyruvate and active acetaldehyde in mitochondria. It plays important roles in the regulation and detoxification of pyruvate metabolism through pyruvate dehydrogenase. We show in this report the inhibitory effect of acetoin on succinate oxidation by Ehrlich tumor cell mitochondria, and thus its regulatory role on intermediate metabolism. Acetoin utilization by Ehrlich mitochondria may lead to small quantities of citrate formation which increase the already increased cholesterol synthesis of cancer cells. Membranes, in particular the inner mitochondrial membrane, flooded with cholesterol, show a proton passive permeability twice as low as that of control mitochondrial membranes, a feature that may be related to drastic changes in membrane potential-dependent metabolism of cancer cells.

Acetoin↗