This study investigated whether conditions known to alter the activity and phosphorylation state of the pyruvate dehydrogenase complex have specific effects on the levels of isoenzymes of pyruvate dehydrogenase kinase (PDK) in rat heart. Immunoblot analysis revealed a remarkable increase in the amount of PDK4 in the hearts of rats that had been starved or rendered diabetic with streptozotocin. Re-feeding of starved rats and insulin treatment of diabetic rats very effectively reversed the increase in PDK4 protein and restored PDK enzyme activity to levels of chow-fed control rats. Starvation and diabetes also markedly increased the abundance of PDK4 mRNA, and re-feeding and insulin treatment reduced levels of the message to that of controls. In contrast with the findings for PDK4, little or no changes in the amounts of PDK1 and PDK2 protein and the abundance of their messages occurred in response to starvation and diabetes. The observed shift in the relative abundance of PDK isoenzymes probably explains previous studies of the effects of starvation and diabetes on heart PDK activity. The results indicate that control of the amount of PDK4 is important in long-term regulation of the activity of the pyruvate dehydrogenase complex in rat heart.

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) 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 Escherichia 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.

Protein phosphatase 2A (PP2A) is a major cellular serine/threonine protein phosphatase, present in the cell in a variety of heterotrimeric forms that differ in their associated regulatory B-subunit. Cloning of the mammalian B subunit has allowed the identification of a highly homologous Saccharomyces cerevisiae gene, RTS1. Disruption of the gene results in a temperaturesensitive growth defect that can be suppressed by expression of rabbit B ␣ or B ␥ isoforms. The B ␣ subunit is much more effective in restoring normal growth at 37°C than B ␥. Immunoprecipitated Rts1p was found associated with type 2A-specific protein phosphatase activity that is sensitive to 2 nM okadaic acid, but not to 100 nM phosphatase inhibitor-2, and to be phosphorylated in vivo. However, overexpression of RTS1 was unable to suppress the cold sensitivity, defective cytokinesis, and abnormal cell morphology resulting from defects in the CDC55 gene, which encodes the yeast homolog of a different B subunit of another form of 2A phosphatase, PP2A 1 . These results indicate that Rts1p is a yeast homolog of the mammalian B subunit and that the various regulatory B-subunits of PP2A are not functionally redundant but direct the enzyme to distinct cellular functions.

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Curcumin [1,7-bis-(4-hydroxy-3-methoxyphenyl)-1,6-heptadiene-3,5-dione, Fig. 1], a compound isolated from Curcuma longa L., has been used for centuries as dietary pigment and spice. Curcumin has been found to possess a variety of traditional pharmaceutical applications on diseases, including external/internal wounds, liver diseases (particularly jaundice), blood purification, microbial effects and inflamed joints.1-4) Over a period of research, curcumin was reported to inhibit carcinogen-induced mutations and the formation of tumour in several experimental systems, 5-7) and exhibit anti-proliferation capability as a potent tool in cancer therapy. 8,9) Curcumin has also been reported to inhibit bacterial lipopolysaccharide-induced TNF-a overexpression and the transcription factor nuclear factor kappa B (NF-kB) activation which are involved in several pathogen-infected diseases. 2,10) Preclinical and clinic studies showed that, however, curcumin possesses several disadvantages in pharmacokinetics such as poor bioavailability, fast metabolism and requiring repetitive oral doses, 11,12) which limited its applications. However, curcumin is still an excellent lead compound for drug design and development on the basis of the explicit bioactivities, non-toxicity and easy synthesis. [13][14][15][16] Curcumin is stable at a pH below 6.5. The instability of curcumin at a pH above 6.5 is caused by the methylene group. 17)Omitting the methylene group and one carbonyl group, B. M. Markaverich, 18) M. Artico, 19) and H. I. El-Subbagh 20) synthesized series of mono-carbonyl curcumin analogues, 1,5-diaryl-1,4-pentadiene-3-ones, and evaluated their bioactivity. The result that the mono-carbonyl analogues exhibit more powerful inhibition in a variety of cancer cells than curcumin indicated that the central methylene group which had been considered the main active group of curcuminoids in antitumor property may be of decreasing importance.Therefore, in the present paper three series of mono-carbonyl curcumin analogues without the central methylene functional groups, 1,5-diaryl-1,4-pentadiene-3-ones (B), together with cyclopentanone (A) and cyclohexanone (C) analogues (Fig. 2), were prepared and their anti-bacterial properties in vitro were evaluated and compared using seven multidrug-resistant bacteria specially causing secondary infections in human being.21) These compounds were also designed to examine the role of different substitutes in the benzene ring and the influence of the space structure of the linking C-strain. It is hoped that continued research will lead to development of new lead compounds from curcumin as antibacterial agents and extrapolated agents for bacteria-infected diseases. Bioreactor and Pharmaceutical Development, Jilin Agricultural University; Changchun 130118, P. R. China. Received August 14, 2007; accepted November 7, 2007 The synthesis of three series of curcumin analogues with mono-carbonyl is described. Their in vitro antibacterial activities against seven Gram-positive and Gram-negative bacteria ...

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