Starvation of lactating rats leads to alterations in the behaviour of pyruvate dehydrogenase kinase which persist in the semi-purified pyruvate dehydrogenase complex of the mammary gland but are partly reversible in vitro

Tissue distribution and kinetic parameters for the four isoenzymes of pyruvate dehydrogenase kinase (PDK1, PDK2, PDK3 and PDK4) identified thus far in mammals were analysed. It appeared that expression of these isoenzymes occurs in a tissue-specific manner. The mRNA for isoenzyme PDK1 was found almost exclusively in rat heart. The mRNA for PDK3 was most abundantly expressed in rat testis. The message for PDK2 was present in all tissues tested but the level was low in spleen and lung. The mRNA for PDK4 was predominantly expressed in skeletal muscle and heart. The specific activities of the isoenzymes varied 25-fold, from 50 nmol/min per mg for PDK2 to 1250 nmol/min per mg for PDK3. Apparent Ki values of the isoenzymes for the synthetic analogue of pyruvate, dichloroacetate, varied 40-fold, from 0.2 mM for PDK2 to 8 mM for PDK3. The isoenzymes were also different with respect to their ability to respond to NADH and NADH plus acetyl-CoA. NADH alone stimulated the activities of PDK1 and PDK2 by 20 and 30% respectively. NADH plus acetyl-CoA activated these isoenzymes nearly 200 and 300%. Under comparable conditions, isoenzyme PDK3 was almost completely unresponsive to NADH, and NADH plus acetyl-CoA caused inhibition rather than activation. Isoenzyme PDK4 was activated almost 2-fold by NADH, but NADH plus acetyl-CoA did not activate above the level seen with NADH alone. These results provide the first evidence that the unique tissue distribution and kinetic characteristics of the isoenzymes of PDK are among the major factors responsible for tissue-specific regulation of the pyruvate dehydrogenase complex activity.

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Activation of Liver X Receptor Regulates Substrate Oxidation in White Adipocytes

Endocrinology ◽

10.1210/en.2009-0676 ◽

2009 ◽

Vol 150 (9) ◽

pp. 4104-4113 ◽

Cited By ~ 36

Author(s):

Britta M. Stenson ◽

Mikael Rydén ◽

Knut R. Steffensen ◽

Kerstin Wåhlén ◽

Amanda T. Pettersson ◽

...

Keyword(s):

Pyruvate Dehydrogenase ◽

Pyruvate Dehydrogenase Complex ◽

Substrate Oxidation ◽

Pyruvate Dehydrogenase Kinase ◽

Tissue Mass ◽

Metabolic Complications ◽

Pyruvate Dehydrogenase Kinase 4 ◽

White Adipocytes ◽

X Receptors

Abstract Liver X receptors (LXRs) are nuclear receptors with established roles in cholesterol, lipid, and carbohydrate metabolism, although their function in adipocytes is not well characterized. Increased adipose tissue mass in obesity is associated with increased adipocyte lipolysis. Fatty acids (FA) generated by lipolysis can be oxidized by mitochondrial β-oxidation, reesterified, or released from the adipocyte. The latter results in higher circulating levels of free FAs, in turn causing obesity-related metabolic complications. However, mitochondrial β-oxidation can at least in part counteract an increased output of FA into circulation. In this study, we provide evidence that activation of LXRs up-regulates mitochondrial β-oxidation in both human and murine white adipocytes. We also show that the expression of a kinase regulating the cellular fuel switch, pyruvate dehydrogenase kinase 4 (PDK4), is up-regulated by the LXR agonist GW3965 in both in vitro differentiated human primary adipocytes and differentiated murine 3T3-L1 cells. Moreover, activation of LXR causes PDK4-dependent phosphorylation of the pyruvate dehydrogenase complex, thereby decreasing its activity and attenuating glucose oxidation. The specificity of the GW3965 effect on oxidation was confirmed by RNA interference targeting LXRs. We propose that LXR has an important role in the regulation of substrate oxidation and the switch between lipids and carbohydrates as cellular fuel in both human and murine white adipocytes.

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On the Specificity of the Herbicide Chlorsulfuron in Intact Spinach Chloroplasts

Zeitschrift für Naturforschung C ◽

10.1515/znc-1985-11-1229 ◽

1985 ◽

Vol 40 (11-12) ◽

pp. 917-918 ◽

Cited By ~ 3

Author(s):

Uwe Homeyer ◽

D. Schulze-Siebert ◽

G. Schultz

Keyword(s):

Fatty Acids ◽

Fatty Acid ◽

Fatty Acid Synthesis ◽

Pyruvate Dehydrogenase ◽

Pyruvate Dehydrogenase Complex ◽

Acid Synthesis ◽

Spinach Chloroplasts ◽

Transamination Reaction ◽

Dehydrogenase Complex

Abstract In vitro incubation of intact spinach chloroplasts with 1 mᴍ Pyruvate was used to study the specificity of action of the herbicide Chlorsulfuron on the synthesis of valine, alanine and fatty acids. As a result, increasing concentrations of the herbicide strongly inhibited valine synthesis while fatty acid synthesis via pyruvate dehydrogenase complex (PDC) and alanine formation by transamination reaction was promoted.

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In vitro synthesis and processing of components of the Ascaris suum pyruvate dehydrogenase complex

Molecular and Biochemical Parasitology ◽

10.1016/0166-6851(88)90113-2 ◽

1988 ◽

Vol 29 (1) ◽

pp. 1-8 ◽

Cited By ~ 8

Author(s):

V RUFF ◽

S DESAI ◽

E DUBRUL ◽

R KOMUNIECKI

Keyword(s):

Pyruvate Dehydrogenase ◽

Ascaris Suum ◽

Pyruvate Dehydrogenase Complex ◽

In Vitro Synthesis ◽

Synthesis And Processing ◽

Dehydrogenase Complex

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Expression and lipoylation in Escherichia coli of the inner lipoyl domain of the E2 component of the human pyruvate dehydrogenase complex

Biochemical Journal ◽

10.1042/bj2890081 ◽

1993 ◽

Vol 289 (1) ◽

pp. 81-85 ◽

Cited By ~ 35

Author(s):

J Quinn ◽

A G Diamond ◽

A K Masters ◽

D E Brookfield ◽

N G Wallis ◽

...

Keyword(s):

Escherichia Coli ◽

Pyruvate Dehydrogenase ◽

Pyruvate Dehydrogenase Complex ◽

Structural Studies ◽

Gene Encoding ◽

E Coli ◽

Inner Lipoyl Domain ◽

Dehydrogenase Complex ◽

Lipoyl Domain

The dihydrolipoamide acetyltransferase subunit (E2p) of mammalian pyruvate dehydrogenase complex has two highly conserved lipoyl domains each modified with a lipoyl cofactor bound in amide linkage to a specific lysine residue. A sub-gene encoding the inner lipoyl domain of human E2p has been over-expressed in Escherichia coli. Two forms of the domain have been purified, corresponding to lipoylated and non-lipoylated species. The apo-domain can be lipoylated in vitro with partially purified E. coli lipoate protein ligase, and the lipoylated domain can be reductively acetylated by human E1p (pyruvate dehydrogenase). Availability of the two forms will now allow detailed biochemical and structural studies of the human lipoyl domains.

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Metabolism of 1-aminoethylphosphinate generates acetylphosphinate, a potent inhibitor of pyruvate dehydrogenase

Biochemical Journal ◽

10.1042/bj2480351 ◽

1987 ◽

Vol 248 (2) ◽

pp. 351-358 ◽

Cited By ~ 22

Author(s):

B Laber ◽

N Amrhein

Keyword(s):

Pyruvate Dehydrogenase ◽

Potent Inhibitor ◽

Pyruvate Dehydrogenase Complex ◽

Anthocyanin Synthesis ◽

Anaerobic Conditions ◽

First Order ◽

Saturation Kinetics ◽

Thiamin Pyrophosphate ◽

Dehydrogenase Complex

The alanine analogue 1-aminoethylphosphinate [H3C-CH(NH2)-PO2H2] effectively inhibited anthocyanin synthesis in buckwheat hypocotyls and caused an increase in the concentrations of alanine and alanine-derived metabolites. Aminotransferase inhibitors partially alleviated the effects of the analogue. 1-Aminoethylphosphinate did not affect the growth of Klebsiella pneumoniae under anaerobic conditions, but under aerobic conditions it inhibited growth and caused the massive excretion of pyruvate. The analogue inhibited the pyruvate dehydrogenase complex in vitro in the presence of an aminotransferase activity. The transamination product of 1-aminoethylphosphinate, acetylphosphinate (H3C-CO-PO2H2), was found to inhibit the pyruvate dehydrogenase complex in a time-dependent reaction that followed first-order and saturation kinetics and required the presence of thiamin pyrophosphate.

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