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PubMed1973

Effects of dichloroacetate on the metabolism of glucose, pyruvate, acetate, 3-hydroxybutyrate and palmitate in rat diaphragm and heart muscle in vitro and on extraction of glucose, lactate, pyruvate and free fatty acids by dog heart in vivo.

1. The extractions of glucose, lactate, pyruvate and free fatty acids by dog heart in vivo were calculated from measurements of their arterial and coronary sinus blood concentration. Elevation of plasma free fatty acid concentrations by infusion of intralipid and heparin resulted in increased extraction of free fatty acids and diminished extractions of glucose, lactate and pyruvate by the heart. It is suggested that metabolism of free fatty acids by the heart in vivo, as in vitro, may impair utilization of these substrates. These effects of elevated plasma free fatty acid concentrations on extractions by the heart in vivo were reversed by injection of dichloroacetate, which also improved extraction of lactate and pyruvate by the heart in vivo in alloxan diabetes. 2. Sodium dichloroacetate increased glucose oxidation and pyruvate oxidation in hearts from fed normal or alloxan-diabetic rats perfused with glucose and insulin. Dichloroacetate inhibited oxidation of acetate and 3-hydroxybutyrate and partially reversed inhibitory effects of these substrates on the oxidation of glucose. In rat diaphragm muscle dichloroacetate inhibited oxidation of acetate, 3-hydroxybutyrate and palmitate and increased glucose oxidation and pyruvate oxidation in diaphragms from alloxan-diabetic rats. Dichloroacetate increased the rate of glycolysis in hearts perfused with glucose, insulin and acetate and evidence is given that this results from a lowering of the citrate concentration within the cell, with a consequent activation of phosphofructokinase. 3. In hearts from normal rats perfused with glucose and insulin, dichloroacetate increased cell concentrations of acetyl-CoA, acetylcarnitine and glutamate and lowered those of aspartate and malate. In perfusions with glucose, insulin and acetate, dichloroacetate lowered the cell citrate concentration without lowering the acetyl-CoA or acetylcarnitine concentrations. Measurements of specific radioactivities of acetyl-CoA, acetylcarnitine and citrate in perfusions with [1-(14)C]acetate indicated that dichloroacetate lowered the specific radio-activity of these substrates in the perfused heart. Evidence is given that dichloroacetate may not be metabolized by the heart to dichloroacetyl-CoA or dichloroacetylcarnitine or citrate or CO(2). 4. We suggest that dichloroacetate may activate pyruvate dehydrogenase, thus increasing the oxidation of pyruvate to acetyl-CoA and acetylcarnitine and the conversion of acetyl-CoA into glutamate, with consumption of aspartate and malate. Possible mechanisms for the changes in cell citrate concentration and for inhibitory effects of dichloroacetate on the oxidation of acetate, 3-hydroxybutyrate and palmitate are discussed.

Acetates↗
PubMed2000

Changes in blood lactate and pyruvate concentrations and the lactate-to-pyruvate ratio during the lactate minimum speed test.

The aim of this study was to assess the responses of blood lactate and pyruvate during the lactate minimum speed test. Ten participants (5 males, 5 females; mean +/- s: age 27.1+/-6.7 years, VO2max 52.0+/-7.9 ml x kg(-1) x min(-1)) completed: (1) the lactate minimum speed test, which involved supramaximal sprint exercise to invoke a metabolic acidosis before the completion of an incremental treadmill test (this results in a 'U-shaped' blood lactate profile with the lactate minimum speed being defined as the minimum point on the curve); (2) a standard incremental exercise test without prior sprint exercise for determination of the lactate threshold; and (3) the sprint exercise followed by a passive recovery. The lactate minimum speed (12.0+/-1.4 km x h(-1)) was significantly slower than running speed at the lactate threshold (12.4+/-1.7 km x h(-1)) (P < 0.05), but there were no significant differences in VO2, heart rate or blood lactate concentration between the lactate minimum speed and running speed at the lactate threshold. During the standard incremental test, blood lactate and the lactate-to-pyruvate ratio increased above baseline values at the same time, with pyruvate increasing above baseline at a higher running speed. The rate of lactate, but not pyruvate, disappearance was increased during exercising recovery (early stages of the lactate minimum speed incremental test) compared with passive recovery. This caused the lactate-to-pyruvate ratio to fall during the early stages of the lactate minimum speed test, to reach a minimum point at a running speed that coincided with the lactate minimum speed and that was similar to the point at which the lactate-to-pyruvate ratio increased above baseline in the standard incremental test. Although these results suggest that the mechanism for blood lactate accumulation at the lactate minimum speed and the lactate threshold may be the same, disruption to normal submaximal exercise metabolism as a result of the preceding sprint exercise, including a three- to five-fold elevation of plasma pyruvate concentration, makes it difficult to interpret the blood lactate response to the lactate minimum speed test. Caution should be exercised in the use of this test for the assessment of endurance capacity.

Adaptation, Physiological↗
PubMed1985

Lactate, pyruvate, and lactate-to-pyruvate ratio during exercise and recovery.

The pattern of lactate increase and its relation to pyruvate and lactate-to-pyruvate (L/P) ratio were studied during exercise and early recovery in 10 normal subjects for incremental exercise on a cycle ergometer. Gas exchange was measured breath by breath. Lactate and pyruvate were measured by enzymatic techniques. Lactate and log lactate changed only slightly at low levels of O2 uptake (VO2) but both began to abruptly increase at approximately 40-55% of the maximal VO2. However, the point of abrupt increase in pyruvate occurred at higher work rates and the rate of increase was not as great as that for lactate. Thus L/P ratio increased at the same VO2 as the log lactate increase. Following the exercise, pyruvate continued to increase steeply for at least the first 5 recovery min, whereas at 2 min lactate increased only slightly or decreased. Thus arterial L/P ratio reversed its direction of change and decreased toward the resting value by 2 min of recovery. Lactate, as well as L/P ratios, decreased in all subjects by 5 min. This study demonstrates that lactate and pyruvate concentrations increase slightly at low levels of exercise without a change in L/P ratio until a threshold work rate at which lactate abruptly increases without pyruvate. The resulting increase in L/P ratio is progressive as work rate is incremented and abruptly reverses when exercise stops.

Adult↗
PubMed2000

Transport of pyruvate in Saccharomyces cerevisiae and cloning of the gene encoded pyruvate permease.

Pyruvate uptake in Saccharomyces cerevisiae was not observed at 0 degrees C and was prevented by the uncoupler carbonyl cyanide m-chlorophenylhydrazone (CCCP). The initial uptake rate of S. cerevisiae kyokai No. 901 was maximum at pH 6 and Km = 4.1 mM. It seemed that lactate inhibited the pyruvate uptake competitively from the results of the Lineweaver-Burk plots. The inhibition constant (Ki) in the presence of 3 mM lactate was 1.6 mM. The pyruvate uptake was inhibited by D-glucose and deoxyglucose, but not by L-glucose, acetate or ethanol. Mutants of laboratory strain No. 5022 ((a) his(2,6), ura3) deficient in pyruvate uptake were isolated from fluoropyruvate resistant mutants. Transformation of the mutant with a yeast genomic library allowed the isolation of the gene JEN1 (YKL217w), which restored pyruvate uptake. Disruption of JEN1 abolished the uptake of pyruvate and gained the resistance against fluoropyruvate. The results indicate that no other monocarboxylate permease is able to efficiently transport pyruvate in S. cerevisiae.

Biological Transport↗
PubMed1976

Identity of kynurenine: pyruvate aminotransferase with histidine: pyruvate aminotransferase.

Kynurenine pyruvate aminotransferase was purified from rat kidney. The purified enzyme had an isoelectric point of pH 5.2 and a pH optimum of 9.3. The enzyme was active with pyruvate as amino acceptor but not with 2-oxoglutarate, and utilized various aromatic amino acids as amino donors. L-Amino acids were effective in the following order of activity: histidine greather than phenylalanine greater than kynurenine greater than tyrosine greater than tryptophan greater than 5-hydroxytryptophan. The apparent Km values were about 0.63 mM, 1.4 mM and 0.09 mM for histidine, kynurenine and phenylalanine, respectively. Km values for pyruvate were 5.5 mM with histidine as amino donor, 1.3 mM with kynurenine and 8.5 mM with phenylalanine. Kynurenine pyruvate aminotransferase activity of the enzyme was inhibited by the addition of histidine or phenylalanine. The molecular weights determined by gel filtration and sucrose density gradient centrifugation were approximately 76000 and 79000, respectively. On the basis of purification ratio, substrate specificity, inhibition by common substrates, subcellular distribution, isoelectric focusing and polyacrylamide-gel electrophoresis, it is suggested that kynurenine pyruvate aminotransferase is identical with histidine pyruvate aminotransferase and also with phenylalanine pyruvate aminotransferase. The physiological significance of the enzyme is discussed.

Animals↗
PubMed1982

Routes of flavodoxin and ferredoxin reduction in Escherichia coli. CoA-acylating pyruvate: flavodoxin and NADPH: flavodoxin oxidoreductases participating in the activation of pyruvate formate-lyase.

Flavodoxin and ferredoxin become reduced in Escherichia coli cells by oxidoreductase reactions which use pyruvate and NADPH as electron donor substrates. The two enzymes, which are minor proteins of this organism, were measured through the reduced flavodoxin-dependent activation of pyruvate formate-lyase. The NADPH-dependent enzyme, obtained homogeneously through Procion-red affinity chromatography, was identified as the flavoprotein 'component R' described previously by Fujii and Huennekens [J. Biol. Chem. 249, 6745-6753 (1974)]. The pyruvate-dependent enzyme was identified as CoA-acetylating pyruvate:flavodoxin (ferredoxin) oxidoreductase. Its catalytic properties in the forward, reverse, and the 14CO2-pyruvate exchange reaction are reported. The dihydro form of flavodoxin was characterized as the particular species involved in the activation of pyruvate formate-lyase. The activation process still occurs with 70% of maximal efficiency when the ratio [NADPH]/([NADP] + [NADPH]) is fixed at the intracellular 'anabolic reduction charge' value of 0.45, in conjunction with the NADPH-dependent enzyme. The [2Fe-2S] ferredoxin, though being readily used as electron acceptor of both oxidoreductases and having a redox potential similar to flavodoxin, proved incompetent in mediating the activation of pyruvate formate-lyase.

Acetyl Coenzyme A↗
PubMed1985

Pyruvate inhibition of pyruvate dehydrogenase kinase is a physiological variable.

Pyruvate inhibited pyruvate dehydrogenase kinase activity in mitochondria from adipose tissue, heart, brain and kidney of fed rats. Starvation for 24 h led to increased kinase activity in mitochondria from adipose tissue and heart but not from brain or kidney and to reduction of pyruvate inhibition of the enzyme from adipose tissue, heart and brain. Insulin injection into starved animals rapidly restored pyruvate inhibition without alteration of kinase activity in adipose tissue and heart mitochondria. Induction of streptozotocin diabetes resulted in loss of pyruvate inhibition of the kinase in heart mitochondria at 48 h but not at 24 h whereas a significant increase of kinase activity was seen at 24 h. It is concluded that the mechanisms which control fluctuations of pyruvate sensitivity of the kinase are different from the mechanisms which control fluctuations of the uninhibited kinase activity.

Adipose Tissue↗
PubMed1986

Avidin as a probe of the conformational changes induced in pyruvate carboxylase by acetyl-CoA and pyruvate.

Sheep liver pyruvate carboxylase was mixed with avidin at a molar ratio of 1:1 in the presence of various combinations of the components of the assay systems required for either the acetyl-CoA-dependent or the acetyl-CoA-independent activity and negatively stained samples were examined by electron microscopy. Significant numbers of chain-like polymers of enzyme-avidin complexes were evident only when acetyl-CoA or high levels of pyruvate were present in the media. Similar results were also obtained for chicken liver pyruvate carboxylase despite this enzyme's almost complete lack of acetyl-CoA-independent activity. Thus, although acetyl-CoA and high concentrations of pyruvate may induce pyruvate carboxylase to adopt a 'tight' tetrahedron-like conformation which can interact with avidin to form chains, this structural change alone does not result in an enzymic form that is maximally active. This suggests that the allosteric activation of pyruvate carboxylase by acetyl-CoA is attributable, at least in part to more subtle conformational changes; especially in the case of the chicken enzyme.

Acetyl Coenzyme A↗
PubMed1976

Identity of isoenzyme 1 of histidine-pyruvate aminotransferase with serine-pyruvate aminotransferase.

After glucagon injection, rats showed virtually identical percentage increases in hepatic histidine-pyruvate aminotransferase and serine-pyruvate aminotransferase activities, both in the mitochondria and in the cytosol. Histidine-pyruvate aminotransferase isoenzyme 1, with pI8.0, was purified to homogeneity from the mitochondrial fraction of liver from glucagon-injected rats. The purified enzyme catalysed transamination between a number of amino acids and pyruvate or phenylpyruvate. For transamination with pyruvate, the activity with serine reached a constant ratio to that with histidine during purification, which was unchanged by a variety of treatments of the purified enzyme. Serine was found to act as a competitive inhibitor of histidine transamination, and histidine of serine transamination. These results suggest that histidine-pyruvate amino-transferase isoenzymes 1 is identical with serine-pyruvate aminotransferase. The enzyme is probably composed of two identical subunits with mol. wt. approx. 38000. The absorbance maximum at 410 nm and the inhibition by carbonyl reagents strongly indicate the presence of pyridoxal phosphate.

Animals↗
PubMed1983

Pathway of oxidation of pyruvic oxime by a heterotrophic nitrifier of the genus Alcaligenes: evidence against hydrolysis to pyruvate and hydroxylamine.

A heterotrophic nitrifier of the genus Alcaligenes, which grows vigorously on pyruvic oxime, was tested by several methods for possible differences or similarities in metabolic performance between pyruvic oxime and its hydrolysis products, pyruvate and hydroxylamine. Major differences were observed between pyruvic oxime and one or both of the other reductants with regard to growth yield, rates of reductant uptake, rates of oxygen uptake, sensitivity of their oxidations to inhibition by thiocyanate, and performance in reductant pulse experiments. Other oximes, some of which are structural analogs of pyruvic oxime and all of which are potential sources of hydroxylamine, were not metabolized by cells or cell-free extract. Collectively the results indicate a pathway of oxidation of pyruvic oxime to nitrite and CO2 that does not involve its initial hydrolysis, but probably involves the oxidation of N and/or C before C-N bond breakage.

Alcaligenes↗
PubMed2006

Flexibility of thiamine diphosphate revealed by kinetic crystallographic studies of the reaction of pyruvate-ferredoxin oxidoreductase with pyruvate.

Pyruvate-ferredoxin oxidoreductases (PFOR) are unique among thiamine pyrophosphate (ThDP)-containing enzymes in giving rise to a rather stable cofactor-based free-radical species upon the decarboxylation of their first substrate, pyruvate. We have obtained snapshots of unreacted and partially reacted (probably as a tetrahedral intermediate) pyruvate-PFOR complexes at different time intervals. We conclude that pyruvate decarboxylation involves very limited substrate-to-product movements but a significant displacement of the thiazolium moiety of ThDP. In this respect, PFOR seems to differ substantially from other ThDP-containing enzymes, such as transketolase and pyruvate decarboxylase. In addition, exposure of PFOR to oxygen in the presence of pyruvate results in significant inhibition of catalytic activity, both in solution and in the crystals. Examination of the crystal structure of inhibited PFOR suggests that the loss of activity results from oxime formation at the 4' amino substituent of the pyrimidine moiety of ThDP.

Anaerobiosis↗
PubMed1979

Pyruvate carboxylase and phosphoenolpyruvate carboxykinase activity in leukocytes and fibroblasts from a patient with pyruvate carboxylase deficiency.

Normal values are given for the activities of pyruvate carboxylase (E.C.6.4.1.1), mitochondrial phosphoenolpyruvate carboxykinase (E.C. 4.1.1.32, PEPCK), and citrate synthase (E.C. 4.1.3.7) in fibroblasts, lymphocytes, and leukocytes. Also given are values for these enzymes in the leukocytes and fibroblasts from a severely mentally and developmentally retarded patient with proximal renal tubular acidosis and hepatic, cerebral, and renal cortical pyruvate carboxylase deficiency. In normals, virtually all of the mitochondrial PEPCK and pyruvate carboxylase activity was present in the mononuclear leukocyte fraction of whole venous blood. Cellular fractionation studies with human lymphocytes and fibroblasts demonstrated that all of the PEPCK activity in these cells is mitochondrial. Normal values for pyruvate carboxylase in leukocytes were 0.092 (0.070--0.208) mU/mg protein (n=5), in lymphocytes 0.154 (0.092--0.262) mU/mg protein (n=5), and in fibroblasts 1.36 (0.778--2.19) mU/mg protein (n=5). The patient with hepatic, renal, and cerebral pyruvate carboxylase deficiency had no detectable activity (less than 0.009 mU/mg protein) in his leukocytes and 0.018 mU/mg protein in his fibroblasts. Data from an assay for pyruvate carboxylase activity in the patient's fibroblasts show that the activity observed is significant but very close to the lower limits of the assay. Values for PEPCK in normal lymphocytes were 1.42 (0.824--1.88) mU/mg protein (n=5), in leukocytes 1.68 (1.64--1.72) mU/mg protein (n=2), and in fibroblasts 5.49 (3.94--6.33) mU/mg protein (n=6).

Acidosis, Renal Tubular↗
PubMed1983

The substrate-mediated inactivation of the pyruvate dehydrogenase component of the pigeon breast muscle pyruvate dehydrogenase complex.

Incubation of the pyruvate dehydrogenase component isolated from the pigeon breast muscle pyruvate dehydrogenase complex with Mg2+, thiamine pyrophosphate and low concentrations of pyruvic acid in the absence of electron acceptors results in irreversible time-dependent inactivation of the enzyme. The rate of the enzyme inactivation is markedly decreased in the presence of high concentrations of pyruvate; in this case acetoin and acetolactate are detected in the reaction mixture. The enzyme activity is stabilized when the artificial electron acceptor, 2,6-dichlorophenolindophenol, is present in the reaction mixture. The substrate-mediated inactivation of the enzyme is accompanied by incorporation of the 2-[14C]-substrate fragment and labelled thiamine pyrophosphate into the protein fraction. The enzyme reactivation by neutral hydroxylamine and the protective effect of dithiothreitol suggest that the SH-group(s) may be involved in the substrate-mediated inactivation of pyruvate dehydrogenase.

Animals↗
PubMed2002

Structure of Escherichia coli pyruvate formate-lyase with pyruvate.

The structure of inactive pyruvate formate-lyase in complex with a natural substrate, pyruvate, was solved at 2.7 A resolution. Both active sites of the homodimeric enzyme are occupied by pyruvate; additional binding sites were not found. Pyruvate was found in a cleft close to the active-site cysteines 418 and 419, with the carboxyl group in contact with arginines 176 and 435 and the methyl group within van der Waals distance of Phe327. It is believed that the binding site of pyruvate is not the position of pyruvate as the reaction initiates, as conformational changes occur during activation of the enzyme.

Acetyltransferases↗
PubMed1993

Molecular cloning and nucleotide sequence of the gene for pyruvate kinase of Bacillus stearothermophilus and the production of the enzyme in Escherichia coli. Evidence that the genes for phosphofructokinase and pyruvate kinase constitute an operon.

Pyruvate kinase from Bacillus stearothermophilus is an allosteric enzyme activated by AMP or ribose 5-phosphate but not by fructose 1,6-bisphosphate. The gene for the enzyme was cloned in Escherichia coli and its entire nucleotide sequence was determined. The deduced amino acid sequence consisted of 587 residues and the molecular mass was calculated to be 62 317 Da. The sequence was highly similar to other pyruvate kinases, indicating that they have the same evolutional origin. Similarly to the E. coli enzymes, the enzyme does not contain an N-terminal domain, in contrast to the eukaryotic pyruvate kinases. However, the Bacillus stearothermophilus enzyme had an extra C-terminal sequence consisting of about 110 amino acid residues. A phosphoenolpyruvate-binding motif, which is observed in pyruvate phosphate dikinase, phosphoenolpyruvate: sugar phosphotransferase system enzyme I and phosphoenolpyruvate synthase, was present in the extra C-terminal sequence. There was an open reading frame upstream of the pyruvate kinase gene. The homology of the sequence showed that the gene encodes phosphofructokinase. Both phosphofructokinase and pyruvate kinase were expressed in E. coli cells, and the evidence suggesting that both genes constitute an operon is presented.

Amino Acid Sequence↗
PubMed2003

Pyruvate shuttle in muscle cells: high-affinity pyruvate transport sites insensitive to trans-lactate efflux.

The specificity of the transport mechanisms for pyruvate and lactate and their sensitivity to inhibitors were studied in L6 skeletal muscle cells. Trans- and cis-lactate effects on pyruvate transport kinetic parameters were examined. Pyruvate and lactate were transported by a multisite carrier system, i.e., by two families of sites, one with low affinity and high capacity (type I sites) and the other with high affinity and low capacity (type II). The multisite character of transport kinetics was not modified by either hydroxycinnamic acid (CIN) or p-chloromercuribenzylsulfonic acid (PCMBS), which exert different types of inhibition. The transport efficiency (TE) ratios of maximal velocity to the trans-activation dissociation constant (Kt) showed that lactate and pyruvate were preferentially transported by types I and II sites, respectively. The cis-lactate effect was observed with high Ki values for both sites. The trans-lactate effect on pyruvate transport occurred only on type I sites and exhibited an asymmetric interaction pattern (Kt of inward lactate > Kt of outward lactate). The inability of lactate to trans-stimulate type II sites suggests that intracellular lactate cannot recruit these sites. The high-affinity type II sites act as a specific pyruvate shuttle and constitute an essential relay for the intracellular lactate shuttle.

4-Chloromercuribenzenesulfonate↗
PubMed2005

Pyruvate dehydrogenase and pyruvate dehydrogenase kinase expression in non small cell lung cancer and tumor-associated stroma.

Pyruvate dehydrogenase (PDH) catalyzes the conversion of pyruvate to acetyl-coenzyme A, which enters into the Krebs cycle, providing adenosine triphosphate (ATP) to the cell. PDH activity is under the control of pyruvate dehydrogenase kinases (PDKs). Under hypoxic conditions, conversion of pyruvate to lactate occurs, a reaction catalyzed by lactate dehydrogenase 5 (LDH5). In cancer cells, however pyruvate is transformed to lactate occurs, regardless of the presence of oxygen (aerobic glycolysis/Warburg effect). Although, hypoxic intratumoral conditions account for HIF1alpha stabilization and induction of anaerobic metabolism, recent data suggest that high pyruvate concentrations also result in HIF1alpha stabilization independently of hypoxia. In the present immunohistochemical study, we provide evidence that the PDH/PDK pathway is repressed in 73% of non small cell lung carcinomas, which may be a key reason for HIF1alpha stabilization and "aerobic glycolysis." However, about half of PDH-HIF pathway, and patients harboring these tumors have an excellent postoperative outcome. A small subgroup of clinically aggressive tumors maintains a coherent PDH and HIF/LDH5 expression. In contrast to cancer cells, fibroblasts in the tumor supporting stroma exhibit an intense PDH but reduced PDK1 expression favoring maximum PDH activity. This means that stroma may use lactic acid produced by tumor cells, preventing the creation of an intolerable intratumoral acidic environment at the same time.

Autopsy↗
PubMed1977

An energy-conserving pyruvate-to-acetate pathway in Entamoeba histolytica. Pyruvate synthase and a new acetate thiokinase.

Under anaerobic conditions, cells of Entamoeba histolytica grown with bacteria produce H2 and acetate while cells grown axenically produce neither. Aerobically, acetate is produced and O2 is consumed by amebae from either type of cells. Centrifuged extracts, 2.4 x 106 x g x min, from both types of cells contain pyruvate synthase (EC 1.2.7.1) and an acetate thiokinase which, together, form a system capable of converting pyruvate to acetate. Pyruvate synthase catalyzes the reaction: pyruvate + CoA leads to CO2 + acetyl-CoA + 2E. Electron acceptors which function with this enzyme are FAD, FMN, riboflavin, ferredoxin, and methyl viologen, but not NAD or NADP. The amebal acetate thiokinase catalyzes the reaction acetyl-CoA + ADP + Pi leads to acetate + ATP + CoA. For this apparently new enzyme we suggest the trivial name acetyl-CoA-synthetase (ADP-forming). Extracts from axenic amebae do not contain hydrogenase, but extracts from cells grown with bacteria do. It is postulated that in bacteria-grown amebae electrons generated at the pyruvate synthase step are utilized anaerobically to produce H2 via the hydrogenase and that the acetyl-CoA is converted to acetate in an energy-conserving step catalyzed by amebal acetyl-CoA synthetase. Aerobically, cells grown under either regimen may utilize the energy-conserving pyruvate-to-acetate pathway since O2 then serves as the ultimate electron acceptor.

Acetate-CoA Ligase↗