Tryptophan fluorescence was used to analyze binding of ligands to human pyruvate dehydrogenase isoform 2 (PDHK2) and to demonstrate effects of ligand binding on distal structure of PDHK2 that is required for binding to the inner lipoyl domain (L2) of the dihydrolipoyl acetyltransferase. Ligand-altered binding of PDHK2 to L2 and effects of specific ligands on PDHK2 oligomeric state were characterized by analytical ultracentrifugation. ATP, ADP, and pyruvate markedly quenched the tryptophan fluorescence of PDHK2 and gave maximum quenching/L 0.5 estimates: ϳ53%/3 M for ATP; ϳ49%/15 M for ADP; and ϳ71%/ϳ590 M for pyruvate. The conversion of Trp-383 to phenylalanine completely removed ATP-and ADP-induced quenching and >80% of the absolute decrease in fluorescence due to pyruvate. The W383F-PDHK2 mutant retained high catalytic activity. Pyruvate, added after ADP, quenched Trp fluorescence with an L 0.5 of 3.4 M pyruvate, >150-fold lower concentration than needed with pyruvate alone. ADP-enhanced binding of pyruvate was maintained with W383F-PDHK2. Binding of PDHK2 dimer to L2 is enhanced when L2 are housed in oligomeric structures, including the glutathione S-transferase (GST)-L2 dimer, and further strengthened by reduction of the lipoyl groups (GST-L2 red ) (Hiromasa and Roche (2003) J. Biol. Chem. 278, 33681-33693). Binding of PDHK2 to GST-L2 red was modestly hindered by 200 M level of ATP or ADP or 5.0 mM pyruvate; a marked change to nearly complete prevention of binding was observed with ATP or ADP plus pyruvate at only 100 M levels, and these conditions caused PDHK2 dimer to associate to a tetramer. These changes should make major contributions to synergistic inhibition of PDHK2 activity by ADP and pyruvate. Ligand-induced changes that interfere with PDHK2 binding to GST-L2 red may involve release of an interdomain cross arm between PDHK2 subunits in which Trp-383 plays a critical anchoring role.Decarboxylation of pyruvate by the mitochondrial pyruvate dehydrogenase complex (PDC) 2 commits glucose and glucose-linked substrates to being either fully oxidized or converted to fatty acids for storage.Because this results in animals in the irrecoverable reduction of body carbohydrate reserves, PDC activity is tightly regulated by dedicated regulatory enzymes (1, 2). The pyruvate dehydrogenase kinase isozymes (PDHK1, PDHK2, PDHK3, and PDHK4) and pyruvate dehydrogenase phosphatase isozymes (PDHP1 and PDHP2) control the fractional activity of PDC in a tissue-specific manner. Phosphorylation of the pyruvate dehydrogenase (E1) component by the PDHKs results in inactivation and dephosphorylation by the PDHPs results in reactivation of E1.The components required in the mammalian complex for the five-step PDC reaction are E1, the dihydrolipoyl acetyltransferase (E2), the dihydrolipoyl dehydrogenase (E3), and the E3-binding protein (E3BP) (1, 2). E2 and E3BP associate via their C-terminal domains to form the pentagonal-dodecahedron shaped core of the complex, a 60-subunit structure with a stoichiometry estimated to be E2 48 E3...

The RNA-binding protein tristetraprolin (TTP) promotes rapid decay of mRNAs bearing 3' UTR AU-rich elements (ARE). In many cancer types, loss of TTP expression is observed allowing for stabilization of ARE-mRNAs and their pathologic overexpression. Here we demonstrate that histone deacetylase (HDAC) inhibitors (Trichostatin A, SAHA and sodium butyrate) promote TTP expression in colorectal cancer cells (HCA-7, HCT-116, Moser and SW480 cells) and cervix carcinoma cells (HeLa). We found that HDAC inhibitors-induced TTP expression, promote the decay of COX-2 mRNA, and inhibit cancer cell proliferation. HDAC inhibitors were found to promote TTP transcription through activation of the transcription factor Early Growth Response protein 1 (EGR1). Altogether, our findings indicate that loss of TTP in tumors occurs through silencing of EGR1 and suggests a therapeutic approach to rescue TTP expression in colorectal cancer.

Removal of organic dyes from water by monolithic adsorbents is considered as an efficient and no-secondary pollution method. Herein, for the first time cordierite honeycomb ceramics (COR) treated with oxalic acid (CORA) were synthesized. This CORA exhibits outstanding removal efficiency toward the azo neutral red dyes (NR) from water. After optimizing the reaction conditions, the highest adsorption capacity of 7.35 mg·g –1 and a removal rate of 98.89% could be achieved within 300 min. Furthermore, investigation of the adsorption kinetics indicated this adsorption process could be described as a pseudo-second-order kinetic model with k 2 and q e of 0.0114 g·mg –1 ·min –1 and 6.94 mg·g –1 , respectively. According to the fitting calculation, the adsorption isotherm could also be described as the Freundlich isotherm model. The removal efficiency could be maintained above 50% after 4 cycles, negating the need for toxic organic solvent extraction, offering a method for bringing the technology one step closer to industrial application and giving CORA promising potential in practical water treatment.

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