Yeast inorganic pyrophosphatase substrate recognition

Monodentate Co(NH₃)₅PP_i was determined not to be a substrate for yeast inorganic pyrophosphatase while P¹,P²-bidentate Co(NH₃)₄PP_i was turned over by the enzyme at a rate of 7.5 min^?1. A kinetic analysis of the substrate activities of the P¹,P²-bidentate complexes, Co(en)₂PP_i, Cr(NH₃)₄PP_i, Cr(H₂O)(NH₃)₃PP_i, Cr(H₂O)₂(NH₃)₂PP_i, and Cr(H₂O)₄PP_i was carried out in order to access the potential role of the metal-water ligands in productive binding. While substitution of the H₂O ligands with NH₃ ligands had a minimal affect on the K_m for Mg²⁺, the binding affinity of the complexes decreased with an increasing $\text{NH}{}_3\text{H}{}_2\text{O}$ ligand ratio as did the turnover number of the corresponding central complexes. The Co(en)₂PP_i complex was hydrolyzed at a rate approximately 0.6% of that for the Co(NH₃)₄PP_i complex. The substrate activities of β,γ-bidentate Co(NH₃)₄PPP_i and α,β,γ-tridentate Co(NH₃)₃PPP with pyrophosphatase were also tested. While both complexes were shown to bind tightly to the Mg²⁺-activated enzyme neither was hydrolyzed. On the other hand, in the presence of the Zn²⁺-activated enzyme the tridentate complex was turned over at a rate of 0.17 min^?1 while the bidentate complex remained inert to hydrolysis.     

Mechanistic studies on metal-pyrophosphate hydrolysis. Structure of tetraammine(chloroaquo)cobalt (III) dichloride ([Co(NH3)4ClH2O]2+.2Cl-), an acid hydrolysis product of Co(NH3)4HP2O7 and Co(NH3)4PO4

The octahedral complex tetraammine(chloroaquo)cobalt(III) dichloride is shown to be the HCl hydrolysis product of both P1,2-bidentate tetraammine(pyrophosphato)cobalt(III) [Co(NH3)4HP2O7 or CoPP] and bidentate tetraammine(phosphato)cobalt(III) [Co(NH3)4PO4 or CoP]. The complex crystallizes in the orthorhombic space group Pna21 with cell dimensions a = 13.033(2)A, b = 6.710(1)A, and c = 10.318(2)A; the crystal structure was refined to a final disagreement index of 0.033. The average of the four Co-N distances is 1.944 +/- 6A. The Co-Cl distance is 2.257(2)A and the Co-O(W) distance is 1.971(4)A. Both protons of the coordinated water molecule are engaged in strong hydrogen bonds to the two nonbonded chloride counterions with O(W)-Cl distances of 3.087(6)A and 3.123(6)A. Each nonbonded chloride is engaged in seven hydrogen bonding interactions resulting from the high ratio of hydrogen bond donors to acceptors in the CoP structure. Cobalt bisphosphate (CoP2) is the final enzyme hydrolysis product when CoPP is used as substrate in the yeast inorganic pyrophosphatase reaction. The bridge oxygen atom is the site of initial CoPP cleavage both for HCl catalyzed hydrolysis as well as for enzyme catalyzed hydrolysis.     

Effect of different extenders on glutamic oxalacetic transaminase (GOT) and glutamic pyruvic transaminase (GPT) release from frozen buffalo semen

Sixty buffalo semen samples (motility greater than 60%) were frozen in 3 extenders, viz., Tris yolk glycerol (TY-G), Citric acid whey glycerol (CAW-G) and Egg yolk glucose sodium bicarbonate glycerol (EYGSB-G) for studying the release of GOT and GPT enzymes in the extracellular fluid during pre-freezing (after first extension) and post-freezing (15 minutes and 30 days after freezing). Release of GOT and GPT enzymes was less in TY-G than CAW-G and EYGSB-G extenders. Significant differences (P<0.01) in GOT and GPT release were observed between extenders and bulls at various stages of freezing of semen.     

Enzymatic dehydration of 3-hydroxymethyloxindole

Crude and partially purified extracts of wheat (Triticum vulgare, red variety) germ catalyze the dehydration of 3-hydroxymethyloxindole to 3-methyleneoxindole. Examination of the ultraviolet absorption spectrum of a reaction mixture consisting of either the extract or partially purified enzyme and 3-hydroxymethyloxindole, shows that this oxindole has undergone complete dehydration to 3-methyleneoxindole. TPNH-linked 3-methyleneoxindole reductase, also a constituent of the wheat germ extract, can be separated from the dehydrase by passage through an Agarose 15 column. Utilizing these partially purified enzymes, it can be demonstrated that the dehydrase activity found in wheat germ is a discrete enzymatic function.     

Photosystem II Independent Carbon Dioxide Fixation in Plectonema boryanum During Photoautotrophic Growth Under Nitrogen Fixation Conditions

The non-heterocystous filamentous cyanobacterium Plectonema boryanum UTEX 594 grew rapidly microaerobically under nitrogen-starvation conditions in continuous high light intensity by conducting oxygenic photosynthesis and oxygen sensitive nitrogen-fixation in alternating cycles. During diazotrophic phase, the light harvesting pigment phycocyanin declined with a concomitant depression in light dependent oxygen evolution by the cyanobacterium. A substantial component of light dependent carbon dioxide fixation during diazotrophic phase was not inhibited by DCMU in spite of complete cessation of photosynthetic oxygen evolution. Endogenous-reductant dependent electron transfer to photosystem I during diazotrophic phase is postulated even during photoautotrophic growth.     

Galangin: A metabolite that suppresses anti-neoplastic activities through modulation of oncogenic targets

With the dramatic increase in cancer incidence all over the world in the last decades, studies on identifying novel efficient anti-cancer agents have been intensified. Historically, natural products have represented one of the most important sources of new lead compounds with a wide range of biological activities. In this article, the multifaceted anti-cancer action of propolis-derived flavonoid, galangin, is presented, discussing its antioxidant, anti-inflammatory, antiproliferative, pro-apoptotic, anti-angiogenic, and anti-metastatic effects in various cancer cells. In addition, co-effects with standard chemotherapeutic drugs as well as other natural compounds are also under discussion, besides highlighting modern nanotechnological advancements for overcoming the low bioavailability issue characteristic of galangin. Although further studies are needed for confirming the anti-cancer potential of galangin in vivo malignant systems, exploring this natural compound might open new perspectives in molecular oncology.     

Radiosensitization of Pancreatic Cancer Cells In Vitro and In Vivo through Poly (ADP-ribose) Polymerase Inhibition with ABT-888

OBJECTIVESTo determine whether poly (ADP-ribose) polymerase-1/2 (PARP-1/2) inhibition enhances radiation-induced cytotoxicity of pancreatic adenocarcinoma in vitro and in vivo, and the mechanism by which this occurs.MethodsPancreatic carcinoma cells were treated with ABT-888, radiation, or both. In vitro cell viability, apoptosis, and PARP activity were measured. Orthotopic xenografts were generated in athymic mice and treated with ABT-888 (25 mg/kg), radiation (5 Gy), both, or no treatment. Mice were monitored with bioluminescence imaging.RESULTSIn vitro, treatment with ABT-888 and radiation led to higher rates of cell death after 8 days (P < .01). Co-treatment with 5 Gy and 1, 10 or 100 μmol/l of ABT-888 led to dose enhancement factors of 1.29, 1.41 and 2.36, respectively. Caspase activity was not significantly increased when treated with ABT-888 (10 μmol/l) alone (1.28-fold, P = .08), but became significant when radiation was added (2.03-fold, P < .01). PARP activity increased post-radiation and was abrogated following co-treatment with ABT-888. In vivo, treatment with ABT-888, radiation or both led to tumor growth inhibition (TGI) of 8, 30 and 39 days, and survival at 60 days of 0%, 0% and 40%, respectively.CONCLUSIONSABT-888 with radiation significantly enhanced tumor response in vitro and in vivo. ABT-888 inhibited PAR protein polymerization resulting in dose-dependent feedback up-regulation of PARP and p-ATM suggesting increased DNA damage. This translated into enhancement in TGI and survival with radiation in vivo. In vitro PAR levels correlated with levels of tumor apoptosis suggesting potential as a predictive biomarker. These data are being used to support a Phase I study in locally advanced pancreatic cancer.     

Biodiesel production using heterogeneous catalysts

The production and use of biodiesel has seen a quantum jump in the recent past due to benefits associated with its ability to mitigate greenhouse gas (GHG). There are large number of commercial plants producing biodiesel by transesterification of vegetable oils and fats based on base catalyzed (caustic) homogeneous transesterification of oils. However, homogeneous process needs steps of glycerol separation, washings, very stringent and extremely low limits of Na, K, glycerides and moisture limits in biodiesel. Heterogeneous catalyzed production of biodiesel has emerged as a preferred route as it is environmentally benign needs no water washing and product separation is much easier. The present report is review of the progress made in development of heterogeneous catalysts suitable for biodiesel production. This review shall help in selection of suitable catalysts and the optimum conditions for biodiesel production.