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PubMed1995

N-acetyl-D-neuraminic acid synthesis in Escherichia coli K1 occurs through condensation of N-acetyl-D-mannosamine and pyruvate.

Two enzymes have been found to be involved in bacterial N-acetyl-D-neuraminic acid (NeuAc) synthesis: NeuAc synthase, which condenses N-acetyl-L,D-mannosamine and phosphoenolpyruvate, and NeuAc lyase or NeuAc aldolase, which condenses N-acetyl-D-mannosamine and pyruvate. When we used Escherichia coli K1 crude extracts, we observed the generation of NeuAc in the presence of N-acetylmannosamine and both phosphoenolpyruvate (NeuAc synthase activity) or pyruvate (NeuAc lyase activity). However, when crude extracts were fractionated by Sephacryl S-200 chromatography, NeuAc synthase activity disappeared. A chromatographic peak of NeuAc synthase activity was detected when column fractions were re-tested in the presence of the active NeuAc lyase peak. Furthermore, crude extracts converted phosphoenolpyruvate into pyruvate. Pyruvate depletion, due to the addition of pyruvate decarboxylase to the NeuAc synthase reaction mixture, blocked NeuAc formation. Moreover, after NeuAc lyase immunoprecipitation no NeuAc synthase was detected. These findings suggest that NeuAc synthase is not present in E. coli K1 and therefore that NeuAc lyase is the only enzyme responsible for NeuAc synthesis in this bacterium.

Escherichia coli↗

PubMed1998

Plant mitochondrial pyruvate dehydrogenase complex: purification and identification of catalytic components in potato.

The pyruvate dehydrogenase complex (mPDC) from potato (Solanum tuberosum cv. Romano) tuber mitochondria was purified 40-fold to a specific activity of 5.60 micromol/min per mg of protein. The activity of the complex depended on pyruvate, divalent cations, NAD+ and CoA and was competitively inhibited by both NADH and acetyl-CoA. SDS/PAGE revealed the complex consisted of seven polypeptide bands with apparent molecular masses of 78, 60, 58, 55, 43, 41 and 37 kDa. N-terminal sequencing revealed that the 78 kDa protein was dihydrolipoamide transacetylase (E2), the 58 kDa protein was dihydrolipoamide dehydrogenase (E3), the 43 and 41 kDa proteins were alpha subunits of pyruvate dehydrogenase, and the 37 kDa protein was the beta subunit of pyruvate dehydrogenase. N-terminal sequencing of the 55 kDa protein band yielded two protein sequences: one was another E3; the other was similar to the sequence of E2 from plant and yeast sources but was distinctly different from the sequence of the 78 kDa protein. Incubation of the mPDC with [2-14C]pyruvate resulted in the acetylation of both the 78 and 55 kDa proteins.

Acetylation↗

PubMed2003

A novel C-terminal proteolytic processing of cytosolic pyruvate kinase, its phosphorylation and degradation by the proteasome in developing soybean seeds.

Cytosolic pyruvate kinase (ATP:pyruvate 2-O-phosphotransferase, EC 2.7.1.40) is an important glycolytic enzyme, but the post-translational regulation of this enzyme is poorly understood. Sequence analysis of the soybean seed enzyme suggested the potential for two phosphorylation sites: site-1 (FVRKGS220DLVN) and site-2 (VLTRGGS407TAKL). Sequence- and phosphorylation state-specific antipeptide antibodies established that cytosolic pyruvate kinase (PyrKinc) is phosphorylated at both sites in vivo. However, by SDS-PAGE, the phosphorylated polypeptides were found to be smaller (20-51 kDa) than the full length (55 kDa). Biochemical separations of seed proteins by size exclusion chromatography and sucrose-density gradient centrifugation revealed that the phosphorylated polypeptides were associated with 26S proteasomes. The 26S proteasome particle in developing seeds was determined to be of approximately 1900 kDa. In vitro, the 26S proteasome degraded associated PyrKinc polypeptides, and this was blocked by proteasome-specific inhibitors such as MG132 and NLVS. By immunoprecipitation, we found that some part of the phosphorylated PyrKinc was conjugated to ubiquitin and shifted to high molecular mass forms in vivo. Moreover, recombinant wild-type PyrKinc was ubiquitinated in vitro to a much greater extent than the S220A and S407A mutant proteins, suggesting a link between phosphorylation and ubiquitination. In addition, during seed development, a progressive accumulation of a C-terminally truncated polypeptide of approximately 51 kDa was observed that was in parallel with a loss of the full-length 55 kDa polypeptide. Interestingly, the C-terminal 51 kDa truncation showed not only pyruvate kinase activity but also activation by aspartate. Collectively, the results suggest that there are two pathways for PyrKinc modification at the post-translational level. One involves partial C-terminal truncation to generate a 51 kDa pyruvate kinase subunit which might have altered regulatory properties and the other involves phosphorylation and ubiquitin conjugation that targets the protein to the 26S proteasome for complete degradation.

Amino Acid Sequence↗

PubMed1999

Characterization of the dihydrolipoamide acetyltransferase of the mitochondrial pyruvate dehydrogenase complex from potato and comparisons with similar enzymes in diverse plant species.

The pyruvate dehydrogenase complex (mPDC) from potato (Solanum tuberosum cv. Romano) can be disassociated in 1 M NaCl and 0.1 M glycine into a large dihydrolipoamide acetyltransferase (E2) complex and smaller pyruvate dehydrogenase (E1) and dihydrolipoamide dehydrogenase (E3) complexes. The E2 complex consists of 55 and 78-kDa polypeptides which are reversibly radiolabelled to a similar degree in the intact mPDC by [2-14C]pyruvate. Affinity-purified antibodies against the 55-kDa protein do not cross-react with the 78-kDa protein and the two proteins show different peptide patterns following partial proteolysis. The 78 and 55-kDa proteins are present in approximately equal abundance in the E2 complex and incorporate a similar amount of [14C] on incubation with [2-14C]pyruvate. Native mPDC and the E2 complex have sedimentation coefficients of 50S and 30S, respectively. Titration of electro-eluted polypeptides against the intact mPDC and E2 complex revealed that each mg of mPDC contains 0.4 mg of E1, 0.4 mg of E2 and 0.2 mg of E3. Labelling of partially purified mPDC from potato, pea, cauliflower, maize and barley, with [2-14C]pyruvate, suggest that a 78-kDa acetylatable protein is only found in the dicotyledonous species, while all plant species tested contained a smaller 52-60 kDa acetylatable protein.

Acetylation↗

PubMed1999

Pyruvate dehydrogenase from Azotobacter vinelandii. Properties of the N-terminally truncated enzyme.

The pyruvate dehydrogenase multienzyme complex (PDHC) catalyses the oxidative decarboxylation of pyruvate and the subsequent acetylation of coenzyme A to acetyl-CoA. Previously, limited proteolysis experiments indicated that the N-terminal region of the homodimeric pyruvate dehydrogenase (E1p) from Azotobacter vinelandii could be involved in the binding of E1p to the core protein (E2p) [Hengeveld, A. F., Westphal, A. H. & de Kok, A. (1997) Eur J. Biochem. 250, 260-268]. To further investigate this hypothesis N-terminal deletion mutants of the E1p component of Azotobacter vinelandii pyruvate dehydrogenase complex were constructed and characterized. Up to nine N-terminal amino acids could be removed from E1p without effecting the properties of the enzyme. Truncation of up to 48 amino acids did not effect the expression or folding abilities of the enzyme, but the truncated enzymes could no longer interact with E2p. The 48 amino acid deletion mutant (E1pdelta48) is catalytically fully functional: it has a Vmax value identical to that of wild-type E1p, it can reductively acetylate the lipoamide group attached to the lipoyl domain of the core enzyme (E2p) and it forms a dimeric molecule. In contrast, the S0.5 for pyruvate is decreased. A heterodimer was constructed containing one subunit of wild-type E1p and one subunit of E1pdelta48. From the observation that the heterodimer was not able to bind to E2p, it is concluded that both N-terminal domains are needed for the binding of E1p to E2p. The interactions are thought to be mainly of an electrostatic nature involving negatively charged residues on the N-terminal domains of E1p and previously identified positively charged residues on the binding and catalytic domain of E2p.

Amino Acid Sequence↗

PubMed1999

Pyruvate and lactate protect striatal neurons against N-methyl-D-aspartate-induced neurotoxicity.

A sustained release of glutamate contributes to neuronal loss during cerebral ischaemia. Using cultured mouse striatal neurons, we observed that glucose deprivation, which occurs in this pathological process, enhanced the N-Methyl-D-aspartate (NMDA)- or alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA)-induced neurotoxicity. The end products of glycolysis, lactate and pyruvate, strongly protected neurons from these neurotoxic effects. The neuroprotective effect of pyruvate (which is more prominent in the absence of glucose) was not related to its ability to react with H2O2 by a decarboxylation process. Pyruvate and L-lactate strongly counteracted the deep decrease in the neuronal ATP content induced by NMDA, indicating that they might protect striatal neurons by rescuing cellular energy charge. Addition of MK-801 after the NMDA withdrawal completely protected neurons, suggesting that NMDA neurotoxicity resulted from a delayed NMDA receptor activation probably linked to a delayed release of an endogenous agonist in the extracellular medium. The strong accumulation of extracellular glutamate which was found in both sham and NMDA-treated cultures was markedly decreased by pyruvate. Thus, pyruvate might also exert its protecting activity by decreasing the delayed accumulation of glutamate which seemed to be neurotoxic only after a preexposure of neurons to NMDA.

Adenosine Triphosphate↗

PubMed1986

Influence of lesions of the limbic-hypothalamic system on metabolic response of pyruvate to daily repeated immobilization stress in rabbits.

The pyruvate metabolic response to the 1st exposure (exposure on the 1st day) to immobilization stress (IMO) were considerably altered by lesions of the periventricular arcuate nucleus (ARC), ventromedial hypothalamus (VMH), stria terminalis (ST) and dorsal fornix (FX). The pyruvate metabolic responses to IMO were completely abolished by seven times repetition of exposure to IMO in the rabbits with lesions of ARC and VMH; they were similar to sham-operated groups. In rabbits with lesions of ST and FX, the pyruvate metabolic responses to the 7th exposure (exposure on the 7th day) to IMO were almost the same as those after the 1st exposure to IMO, but these metabolic responses were completely abolished by the seven times repetition of exposure to IMO in the sham-operated animals. These results suggest that firstly the ARC, VMH, amygdala (AMYG)-ST system and dorsal hippocampus (HPC)-FX system are involved in the pyruvate metabolic responses to the 1st exposure to IMO, and secondly, that the AMYG-ST system and the HPC-FX system are involved in the disappearance process of pyruvate metabolic responses to IMO by the daily repetition of exposure to IMO.

Animals↗

PubMed1984

In vitro and in situ skeletal muscle pyruvate dehydrogenase activity in adrenalectomized and glucocorticoid treated rats.

Skeletal muscle glucose oxidation is significantly reduced and alanine release enhanced in adrenalectomized rats after short-term glucocorticoid treatment. A possible site of regulation is the pyruvate dehydrogenase complex. Pyruvate dehydrogenase activity was measured in vitro in extracts of the gastrocnemius muscle of normal, adrenalectomized and short-term glucocorticoid treated rats by the p-nitroaniline-arylamine-acetyltransferase method and in situ in non-recirculating perfusions of isolated hindlimbs with physiological pyruvate levels and tracer doses of [1-14C] pyruvate by measuring the off-kinetic of 14CO2 wash out in the effluent. Neither method showed a direct influence of glucocorticoids on skeletal muscle pyruvate dehydrogenase activity.

Adrenal Glands↗

PubMed1981

Short term regulation of mouse pyruvate dehydrogenase complex by insulin.

Pyruvate dehydrogenase complex activity and its regulating factors were measured in diabetic mice in a starved or unstarved state. Both in starved and unstarved groups of normal mice, pyruvate dehydrogenase complex activity increased equally by insulin administration. On the other hand, in an unstarved group of diabetic mice, no change in pyruvate dehydrogenase complex activity was observed with the same treatment. With the starved group it increased within 10 minutes and recovered to the base value level in 30 minutes. As a result of studies on active form of pyruvate dehydrogenase complex in the liver and its regulating factors, it was found that no corresponding relation existed between the enzyme complex activity and its regulating factors. We found that unlike the normal mice, not only the previously known regulating mechanism but also other factors affected the pyruvate dehydrogenase complex activity in the diabetic mice.

Animals↗

PubMed1969

Alpha-keto acid dehydrogenase complexes. XI. Comparative studies of regulatory properties of the pyruvate dehydrogenase complexes from kidney, heart, and liver mitochondria.

The activity of the multienzyme pyruvate dehydrogenase complexes, isolated from mitochondria of beef kidney, beef heart, and pork liver, is regulated by phosphorylation and dephosphorylation. Phosphorylation and concomitant inactivation of each of the three complexes are catalyzed by an ATP-specific kinase, and dephosphorylation and concomitant reactivation are catalyzed by a phosphatase. The phosphatase has been separated from the other component enzymes of each pyruvate dehydrogenase complex, and the three phosphatases are functionally interchangeable. The kinase has been isolated from the beef kidney complex, and it is functional with the beef heart and pork liver complexes. ADP is competitive with ATP, and the ADP effect is more pronounced with the kidney kinase than with the liver and heart kinases. Pyruvate protects strongly the heart and liver pruvate dehydrogenase complexes and, to a lesser extent, the kidney complex against inactivation by ATP. Pyruvate apparently exerts its effect on the pyruvate dehydrogenase component of the complex, rather than on the kinase.

Adenine Nucleotides↗

PubMed1970

Interconversion of phospho- and dephospho- forms of pig heart pyruvate dehydrogenase.

Pyruvate dehydrogenase from pig heart exists in active and inactive forms. Interconversion from the active (dephospho) form into the inactive (phospho) form is catalyzed by an ATP-dependent kinase. Conversely the enzyme is reactivated by a phosphatase which removes the phosphate group from the protein. By gradient centrifugation pyruvate dehydrogenase was prepared free of phosphatase but still containing the kinase. Reactivation of pyruvate dehydrogenase is stimulated by adenosine 3',5'-cyclic phosphate. There is incorporation of (32)P from gamma-(32)P-ATP into the protein fraction containing the phosphatase and this phosphorylation reaction is also stimulated by adenosine 3',5'-cyclic phosphate. The participation of this phosphate in the pyruvate dehydrogenase interconversion system suggests that, in heart muscle, pyruvate oxidation may be under hormonal control by a mechanism similar to that involved in the regulation of glycogen synthesis and breakdown.

Adenine Nucleotides↗

PubMed1972

Reversibility of the tryptophanase reaction: synthesis of tryptophan from indole, pyruvate, and ammonia.

Degradation of tryptophan to indole, pyruvate, and ammonia by tryptophanase (EC 4....) from Escherichia coli, previously thought to be an irreversible reaction, is readily reversible at high concentrations of pyruvate and ammonia. Tryptophan and certain of its analogues, e.g., 5-hydroxytryptophan, can be synthesized by this reaction from pyruvate, ammonia, and indole or an appropriate derivative at maximum velocities approaching those of the degradative reactions. Concentrations of ammonia required for the synthetic reactions produce specific changes in the spectrum of tryptophanase that differ from those produced by K(+) and indicate that ammonia interacts with bound pyridoxal 5'-phosphate to form an imine. Kinetic results indicate that pyruvate is the second substrate bound, hence indole must be the third. These results favor a modified mechanism for the multitude of tryptophanase-catalyzed reactions in which alpha-aminoacrylate, which functions as a common enzyme-bound intermediate in both synthetic and degradative reactions, is not released into the medium during the latter reactions, but is degraded to pyruvate and ammonia by sequential reversible steps via enzyme-bound intermediates.

Acrylates↗

PubMed1974

Adenylate cyclase from Brevibacterium liquefaciens. III. In situ regulation of adenylate cyclase by pyruvate.

In the presence of DL-alanine intracellular cyclic AMP in nonproliferating cells of Brevibacterium liquefaciens increased rapidly to the maximum level of approximately 180 muM, and extracellular cyclic AMP increased to 100 muM within 4 hr at 25 degrees . Adenylate cyclase (EC 4.6.1.1) induction was not observed during this incubation. The concentration of pyruvate in the total culture increased concomitantly with that of cyclic AMP and reached approximately 20 mM after 4 hr of incubation. Since the activity of cyclic nucleotide phosphodiesterase is extremely low in this bacterium, the accumulation of cyclic AMP with DL-alanine appeared to be due to the activation of adenylate cyclase by pyruvate. D-alanine was more effective than L-alanine in producing pyruvate, and a high activity of D-alanine oxidation was detected in the cell lysate of B. liquefaciens.Thus, adenylate cyclase in this bacterium appeared to be regulated in vivo by pyruvate which was formed, in this case, predominantly from D-alanine through the action of D-aminoacid oxidase (EC 1.4.3.3). Pyruvate, added extracellularly, also caused a rapid accumulation of intracellular cyclic AMP. Glucose did not change the level of cyclic AMP significantly. It also did not affect the intracellular accumulation of cyclic AMP with DL-alanine.

Adenylyl Cyclases↗

PubMed1975

Structural properties of pyruvate carboxylases from chicken liver and other sources.

Varieties of pyruvate carboxylase [pyruvate: CO2 ligase (ADP-forming), EC 6.4.1.1] obtained from the livers of several species of vertebrates, including humans, all show the same basic structure. They are composed of large polypeptide chains of molecular weights ranging from 1.2 to 1.3 X 10(5) for the different varieties of the enzyme. The native form of the enzyme appears to be a tetramer with a molecular weight of about 5 X 10(5). In the case of pyruvate carboxylase from chicken liver each polypeptide chain contains a biotin moiety, thus supporting the thesis that the tetramer contains four identical polypeptide chains. Pyruvate carboxylase from yeast appears to be basically similar to those from the vertebrate species and has a tetrameric structure. Each protomer contains a single polypeptide chain with a molecular weitht of 1.25 X 10(5). In contrast, pyruvate carboxylase from two bacterial species, Pseudomonas citronellolis and Axotobacter vinelandii, appears to be a dimer with a molecular weight (2.5 X 10(5)) about half that of the animal and yeast species. As a further difference, each of the protomers of the bacterial enzymes contain two polypeptides of 6.5 and 5.4 X 10(5) molecular weight in case of the Pseudomonas enzyme. The larger of the two polypeptides contains the biotin moiety. The functional units of the bacterial enzyme thus appear to contain two polypeptides while that of the liver and yeast enzymes is made up of a single chain. Neither of these arrangements corresponds with those of other biotin enzymes whose structure has been extensively studied (acetyl-CoA carboxylases from liver or Excherichia coli, and transcarboxylase from Propionibacterium).

Animals↗

PubMed1980

Activation of pyruvate dehydrogenase by direct addition of insulin to an isolated plasma membrane/mitochondria mixture: evidence for generated of insulin's second messenger in a subcellular system.

The addition of insulin to a mixture of plasma membrane and mitochondrial fractions from rat adipocytes results in a decrease in the phosphorylation of a mitochondrial protein identified as the alpha subunit of pyruvate dehydrogenase [pyruvate:lipoamide oxidoreductase (decarboxylating and acceptor-acetylating), EC 1.2.4.1] (Seals, J. R., McDonald, J. M. & Jarett, L. (1979) J. Biol. Chem. 254, 6991-6996). This study confirms the prediction that a corresponding increase in pyruvate dehydrogenase activity can be effected by insulin treatment of this preparation. Incubation of the plasma membrane/mitochondria mixture with ATP inhibited pyruvate dehydrogenase activity as measured in a subsequent enzyme assay. The presence of insulin during this incubation with ATP resulted in a 24.5% stimulation of enzyme activity compared to incubation without insulin (n = 9, P < 0.001). The effect was specific for biologically active insulin and was insulin dose-dependent in the physiological range of insulin. Supermaximal doses of insulin produced reduced effects. An insulin effect of similar magnitude could also be observed when the plasma membrane/mitochondria mixture was incubated without ATP. Two insulin mimickers, concanavalin A and antibody to insulin receptor, stimulated pyruvate dehydrogenase by 30.4% (n = 6, P <0.001) and 28.1% (n = 8, P<0.001), respectively. Both of these agents also produced reduced effects at supermaximal concentrations. The effects of all three agents required plasma membranes and could not be produced by treatment of mitochondria alone. The results suggest that a mechanism common to all three agents is responsible for transmitting the stimulation from the plasma membrane to the mitochondrial components of the mixture.

Adipose Tissue↗

PubMed1982

Regulation of pyruvate dehydrogenase kinase activity by protein thiol-disulfide exchange.

Endogenous kinase activity of highly purified pyruvate dehydrogenase complex from bovine kidney is markedly inhibited by N-ethylmaleimide and by certain disulfides. Inhibition by disulfides is highly specific and is reversed by thiols. 5,5'-Dithiobis(2-nitrobenzoate) is the most potent inhibitor, showing significant inhibition at a concentration as low as 1 microM. Cystamine, oxidized glutathione, pantethine, lipoic acid, lipoamide, ergothionine, insulin, oxytocin, and vasopressin were ineffective. Hydrogen peroxide and t-butyl hydroperoxide were inactive. The data indicate pyruvate dehydrogenase kinase (EC 2.7.1.99) contains a thiol group (or groups) that is involved in maintaining a conformation of the enzyme that facilitates phosphorylation and inactivation of its protein substrate, pyruvate dehydrogenase (EC 1.2.4.1). These findings suggest that modulation of pyruvate dehydrogenase kinase activity by thiol-disulfide exchange may be an important physiological mechanism for regulation of kinase activity and, hence, activity of the pyruvate dehydrogenase complex.

Animals↗

PubMed1989

Cytosolic thyroid hormone-binding protein is a monomer of pyruvate kinase.

A cDNA clone encoding a human cytosolic thyroid hormone-binding protein (p58) has been isolated. The human sequence was found to be homologous to that of rat pyruvate kinase (EC 2.7.1.40) subtype M2. p58 is a monomer that has approximately 5% the enzymatic activity of the tetrameric pyruvate kinase M2. The tetrameric M2 does not bind 3,3',5-triiodo-L-thyronine (T3). Binding of p58 to T3 and its analogs resulted in the inhibition of its pyruvate kinase activity. The apparent Ki values of T3, L-thyroxine, and D-T3 are 30 nM, 100 nM, and 2 mM, respectively. L-Thyronine and 3,3',5'-triiodo-L-thyronine had no effect. This order of activity correlates with the thermogenic effects reported for T3 and its analogs. Conversion of p58 to the tetramer is reversible and is under the control of fructose 1,6-bisphosphate. The conversion is inhibited by T3 in a dose-dependent manner. Since pyruvate kinase is a key enzyme in regulating cellular ADP, ATP, and pyruvate, our findings suggest that p58 may be involved in mediating some of the cellular metabolic effects induced by thyroid hormones.

Amino Acid Sequence↗

PubMed1995

Diversity of the pyruvate dehydrogenase kinase gene family in humans.

Recent evidence from this laboratory indicates that at least two isoenzymic forms of pyruvate dehydrogenase kinase (PDK1 and PDK2) may be involved in the regulation of enzymatic activity of mammalian pyruvate dehydrogenase complex by phosphorylation (Popov, K.M., Kedishvili, N.Y., Zhao, Y., Gudi, R., and Harris, R.A. (1994) J. Biol. Chem. 269, 29720-29724). The present study was undertaken to further explore the diversity of the pyruvate dehydrogenase kinase gene family. Here we report the deduced amino acid sequences of three isoenzymic forms of PDK found in humans. In terms of their primary structures, two isoenzymes identified in humans correspond to rat PDK1 and PDK2, whereas a third gene (PDK3) encodes for a new isoenzyme that shares 68% and 67% of amino acid identities with PDK1 and PDK2, respectively. PDK3 cDNA expressed in Eschierichia coli directs the synthesis of a polypeptide with a molecular mass of approximately 45,000 Da that possesses catalytic activity toward kinase-depleted pyruvate dehydrogenase. PDK3 appears to have the highest specific activity among the three isoenzymes tested as recombinant proteins. Tissue distribution of all three isoenzymes of human PDK was characterized by Northern blot analysis. The highest amount of PDK2 mRNA was found in heart and skeletal muscle, the lowest amount in placenta and lung. Brain, kidney, pancreas, and liver expressed an intermediate amount of PDK2 (brain > kidney = pancreas > liver). The tissue distribution of PDK1 mRNA differs markedly from PDK2. The message for PDK1 was expressed predominantly in heart with only modest levels of expression in other tissues (skeletal muscle > liver > pancreas > brain > placenta = lung > kidney). In contrast to PDk1 and PDK2, which are expressed in all tissues tested, the message for PDK3 was found almost exclusively in heart and skeletal muscle, indicating that PDK3 may serve specialized functions characteristic of muscle tissues. In all tissues tested thus far, the level of expression of PDK2 mRNA was essentially higher than that of PDK1 and PDK3, consistent with the idea that PDK2 is a major isoenzyme responsible for regulation of pyruvate dehydrogenase in human tissues.

Amino Acid Sequence↗