Mitochondrial Pyruvate Dehydrogenase (Molecular Cloning of the E1[alpha] Subunit and Expression Analysis)

Grof, Christopher P. L.; Winning, Brenda M.; Scaysbrook, T.; Hill, Steven A.; Leaver, Christopher J.

doi:10.1104/pp.108.4.1623

Cited by 17 publications

(7 citation statements)

References 29 publications

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“…A similar pattern was observed in an earlier study of the phosphorylation state of mtPDC in pea seedlings [51]. As was found with the plPDC subunits, mtPDC is highly expressed in pollen [52,53].…”

Section: Expression Of Mtpdcsupporting

confidence: 84%

Regulation of pyruvate dehydrogenase complex activity in plant cells

Tovar‐Méndez¹,

Miernyk²,

Randall³

2003

European Journal of Biochemistry

273

194

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The pyruvate dehydrogenase complex (PDC) is subjected to multiple interacting levels of control in plant cells. The first level is subcellular compartmentation. Plant cells are unique in having two distinct, spatially separated forms of the PDC; mitochondrial (mtPDC) and plastidial (plPDC). The mtPDC is the site of carbon entry into the tricarboxylic acid cycle, while the plPDC provides acetyl-CoA and NADH for de novo fatty acid biosynthesis. The second level of regulation of PDC activity is the control of gene expression. The genes encoding the subunits of the mt-and plPDCs are expressed following developmental programs, and are additionally subject to physiological and environmental cues. Thirdly, both the mt-and plPDCs are sensitive to product inhibition, and, potentially, to metabolite effectors. Finally, the two different forms of the complex are regulated by distinct organelle-specific mechanisms. Activity of the mtPDC is regulated by reversible phosphorylation catalyzed by intrinsic kinase and phosphatase components. An additional level of sensitivity is provided by metabolite control of the kinase activity. The plPDC is not regulated by reversible phosphorylation. Instead, activity is controlled to a large extent by the physical environment that exists in the plastid stroma.

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Section: Expression Of Mtpdcsupporting

confidence: 84%

Regulation of pyruvate dehydrogenase complex activity in plant cells

Tovar‐Méndez¹,

Miernyk²,

Randall³

2003

European Journal of Biochemistry

273

194

View full text Add to dashboard Cite

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“…The N-terminal amino acid sequences of the 43 and 41 kDa proteins were identical and matched a sequence beginning 27 residues from the start codon of a predicted amino acid sequence derived from a full-length cDNA clone (accession number GB Z26949) encoding E1α of mPDC from potato [12]. It is not clear whether the 43 and 41 kDa proteins in the purified potato mPDC represent isoenzymes of E1α, the products of C-terminal proteolysis of a single polypeptide or differential post-transcriptional processing products.…”

Section: Protein Gel Electrophoresis and N-terminal Sequencing Of Potmentioning

confidence: 86%

“…Further attempts to identify the components of plant mPDC have used antibodies raised against mammalian, yeast and several plant mPDC polypeptides. The E1α component has been identified as a 41-43 kDa protein on the basis of reaction with antibodies raised against E1α from mammals, yeast and Zea mays [11][12][13] and on the basis of phosphorylation studies [14,15]. Using anti-(pig mPDC E3) antibodies the E3 component in pea mitochondria had been identified as a 58 kDa protein [1] or a 67 kDa [11] protein.…”

Section: Introductionmentioning

confidence: 99%

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

MILLAR

Knorpp

Leaver

et al. 1998

Biochemical Journal

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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.

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“…Grof et al (1995) studied the development of the E1␣-subunit of pyruvate dehydrogenase during cucumber seedling development. It has been shown that this subunit undergoes lightdependent inactivation by phosphorylation to potentially limit the activity of the TCA cycle during photorespiration (Gemel and Randall, 1992).…”

Section: Discussionmentioning

confidence: 99%

“…These data suggest that new carbon fixation by photosynthesis is required for full TCA cycle activity. Recently, it was suggested that the TCA cycle may be limited postgerminatively by transcriptional control of mitochondrial pyruvate dehydrogenase (Grof et al, 1995).…”

mentioning

confidence: 99%

Metabolic Bypass of the Tricarboxylic Acid Cycle during Lipid Mobilization in Germinating Oilseeds1

et al. 1998

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Upon germination of oilseeds, storage triacylglycerols are mobilized by conversion to carbohydrates for transport to the root and shoot axes of the developing seedling. Suc, the major carbohydrate transport form, is used as a substrate for biosynthesis and is respired for energy. Lipid mobilization in postgerminative oilseeds requires the metabolic coordination of four subcellular compartments: the oil body, the glyoxysome, the mitochondrion, and the cytosol (Trelease and Doman, 1984). The elucidation of this complex interaction was dependent on the discovery of the glyoxylate cycle (Kornberg and Krebs, 1957). Fatty acids are cleaved by lipases from their glycerol backbone in the oil body and, after being transported to the glyoxysome, are degraded by ␤-oxidation to acetyl-CoA. The glyoxylate cycle ultimately catalyzes the condensation of two of these acetyl-CoA molecules to form succinate, which is then transported to the mitochondrion and metabolized by a partial TCA cycle. Since the complete TCA cycle catalyzes two decarboxylative reactions, the quantitative conversion of lipid to Suc can occur only if certain TCA cycle reactions are bypassed. During gluconeogenesis, only the TCA cycle activities of succinate dehydrogenase, fumarase, and malate dehydrogenase are required. The activities of the TCA cycle decarboxylative enzymes NAD ϩ -IDH and ␣-ketoglutarate dehydrogenase are avoided.Flux through the TCA cycle in plant tissues can vary, depending on the metabolic requirements of the tissue. For example, a reduction in the activity of the TCA cycle in the light compared with its activity in the dark has been documented (Gemel and Randall, 1992;Hanning and Heldt, 1993). The TCA cycle is regulated by the redox state of the pyridine nucleotide pool (Oliver and McIntosh, 1995). NADH competitively inhibits the activities of NAD ϩ -IDH, ␣-ketoglutarate dehydrogenase, and pyruvate dehydrogenase (although technically not a component of the TCA cycle, the pyruvate dehydrogenase complex is the entry point of glycolytically derived pyruvate into the TCA cycle). Furthermore, NAD ϩ -IDH is noncompetitively inhibited by NADPH (McIntosh and Oliver, 1992). The regulation of the TCA cycle in plants differs from its regulation in animals in that none of the plant enzymes appears to be controlled by ratios of adenine nucleotides, e.g. the ratio of ATP/ADP or of acetyl-CoA/CoA (Voet and Voet, 1990; Oliver and McIntosh, 1995).The proposed TCA cycle bypass was first demonstrated by in vivo labeling studies in castor bean endosperm (Canvin and Beevers, 1961). Radiolabeled acetate was shown to be converted into carbohydrate with an experimental efficiency of 70% for the methyl carbon of acetate and 30% for the carboxyl carbon of acetate. The efficiency of conversion was lower for the carboxyl carbon because it is this carbon that is lost from succinate at the reaction of PEP carboxykinase, the only decarboxylative step of gluconeogenesis. In 1 This research was supported by the National Science Foundation (grant IBN-9696154) and is a...

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Mitochondrial Pyruvate Dehydrogenase (Molecular Cloning of the E1[alpha] Subunit and Expression Analysis)

Cited by 17 publications

References 29 publications

Regulation of pyruvate dehydrogenase complex activity in plant cells

Regulation of pyruvate dehydrogenase complex activity in plant cells

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

Metabolic Bypass of the Tricarboxylic Acid Cycle during Lipid Mobilization in Germinating Oilseeds1

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