Differential induction, purification and characterization of cold active lipase from Yarrowia lipolytica NCIM 3639

The production, purification and characterization of cold active lipases by Yarrowia lipolytica NCIM 3639 is described. The study presents a new finding of production of cell bound and extracellular lipase activities depending upon the substrate used for growth. The strain produced cell bound and extracellular lipase activity when grown on olive oil and Tween 80, respectively. The organism grew profusely at 20 °C and at initial pH of 5.5, producing maximum extracellular lipase. The purified lipase has a molecular mass of 400 kDa having 20 subunits forming a multimeric native protein. Further the enzyme displayed an optimum pH of 5.0 and optimum temperature of 25 °C. Peptide mass finger printing reveled that some peptides showed homologues sequence (42%) to Yarrowia lipolytica LIP8p. The studies on hydrolysis of racemic lavandulyl acetate revealed that extracellular and cell bound lipases show preference over the opposite antipodes of irregular monoterpene, lavandulyl acetate.     

Novel anti-inflammatory activity of epoxyazadiradione against macrophage migration inhibitory factor: inhibition of tautomerase and proinflammatory activities of macrophage migration inhibitory factor

Macrophage migration inhibitory factor (MIF) is responsible for proinflammatory reactions in various infectious and non-infectious diseases. We have investigated the mechanism of anti-inflammatory activity of epoxyazadiradione, a limonoid purified from neem (Azadirachta indica) fruits, against MIF. Epoxyazadiradione inhibited the tautomerase activity of MIF of both human (huMIF) and malaria parasites (Plasmodium falciparum (PfMIF) and Plasmodium yoelii (PyMIF)) non-competitively in a reversible fashion (K(i), 2.11-5.23 μm). Epoxyazadiradione also significantly inhibited MIF (huMIF, PyMIF, and PfMIF)-mediated proinflammatory activities in RAW 264.7 cells. It prevented MIF-induced macrophage chemotactic migration, NF-κB translocation to the nucleus, up-regulation of inducible nitric-oxide synthase, and nitric oxide production in RAW 264.7 cells. Epoxyazadiradione not only exhibited anti-inflammatory activity in vitro but also in vivo. We tested the anti-inflammatory activity of epoxyazadiradione in vivo after co-administering LPS and MIF in mice to mimic the disease state of sepsis or bacterial infection. Epoxyazadiradione prevented the release of proinflammatory cytokines such as IL-1α, IL-1β, IL-6, and TNF-α when LPS and PyMIF were co-administered to BALB/c mice. The molecular basis of interaction of epoxyazadiradione with MIFs was explored with the help of computational chemistry tools and a biological knowledgebase. Docking simulation indicated that the binding was highly specific and allosteric in nature. The well known MIF inhibitor (S,R)-3-(4-hydroxyphenyl)-4,5-dihydro-5-isoxazole acetic acid methyl ester (ISO-1) inhibited huMIF but not MIF of parasitic origin. In contrast, epoxyazadiradione inhibited both huMIF and plasmodial MIF, thus bearing an immense therapeutic potential against proinflammatory reactions induced by MIF of both malaria parasites and human.     

Structural studies on 10-hydroxygeraniol dehydrogenase: A novel linear substrate-specific dehydrogenase from Catharanthus roseus

Conversion of 10-hydroxygeraniol to 10-oxogeranial is a crucial step in iridoid biosynthesis. This reaction is catalyzed by a zinc-dependent alcohol dehydrogenase, 10-hydroxygeraniol dehydrogenase, belonging to the family of medium-chain dehydrogenase/reductase (MDR). Here, we report the crystal structures of a novel 10-hydroxygeraniol dehydrogenase from Catharanthus roseus in its apo and nicotinamide adenine dinucleotide phosphate (NADP⁺) bound forms. Structural analysis and docking studies reveal how subtle conformational differences of loops L1, L2, L3, and helix α9' at the orifice of the catalytic site confer differential activity of the enzyme toward various substrates, by modulating the binding pocket shape and volume. The present study, first of its kind, provides insights into the structural basis of substrate specificity of MDRs specific to linear substrates. Furthermore, comparison of apo and NADP⁺ bound structures suggests that the enzyme adopts open and closed states to facilitate cofactor binding.     

Transformation of a monoterpene ketone, piperitenone, and related terpenoids using Mucor piriformis

Biotransformation of piperitenone (I), 5,5-dimethyl-2-(1-methylethylidene)-cyclohexanone (II), and 2-(1-ethyl-1-propylidene)-5-methylcyclohexanone (III) was studied using a versatile fungal strain, Mucor piriformis. The organism initiates transformation of these compounds by hydroxylation at the allylic positions or at the tertiary carbon. Transformation of piperitenone (I) by this strain yielded 5-hydroxypiperitenone (Ic), 7-hydroxypiperitenone (Id), 7-hydroxypulegone (Ie), 10-hydroxypiperitenone (If), and 4-hydroxypiperitenone (Ig) as metabolites. It was possible to block some of the metabolic activities of the organism through structural modification of piperitenone (I). This was evidenced by the fact that biotransformation of 5,5-dimethyl-2-(1-methylethylidene)-cyclohexanone (II) yielded 5,5-dimethyl-2-(1-hydroxy-1-methylethyl)-2-cyclohexen-1-one (IIb) and 5,5-dimethyl-3-hydroxy-2-(1-methylethylidene)-cyclohexanone (IIa), whereas 2-(1-ethyl-1-propylidene)-5-methylcyclohexanone (III) yielded 6-(1-ethyl-1-propylidene)-5-methyl-2-cyclohexen-1-one (IIIb) and 6-(1-ethyl-1-propylidene)-5-hydroxy-5-methylcyclohexanone (IIIa) as metabolites. Based on the identification of the metabolites, pathways for the biotransformation of I, II, and III have been proposed. The mode of biotransformation of these compounds by M. piriformis also compared to their modes of metabolism in the rat system.     

Regioselective and efficient enzymatic synthesis of antimicrobial andrographolide derivatives

Labdane diterpene andrographolide (1) is a major constituent of Andrographis paniculata and known to exhibit wide spectrum of biological activities. In this study, regioselective monoesters of (1) have been synthesized by using Amano lipase AK (Pseudomonas fluorescens) as a biocatalyst. Amano lipase AK was able to execute highly efficient esterification of hydroxyl group attached to C-14 carbon of (1) in presence of acyl donors. Among the various synthesized derivatives including two novel compounds such as andrographolide-14-propionate (3) and andrographolide-14-caproate (5) displayed antimicrobial activity against Staphylococcus aureus with low minimal inhibitory concentration (MIC) 4?µg/mL and 16?µg/mL respectively. Furthermore, they have shown low hemolysis activity at their respective MIC and increase in the permeability of the bacterial cell membrane as delineated by FITC uptake and SEM imaging studies.     

Andrographolide Inhibits Osteopontin Expression and Breast Tumor Growth Through Down Regulation of PI3 Kinase/Akt Signaling Pathway

Breast cancer is one of the most common cancers among women in India and around the world. Despite recent advancement in the treatment of breast cancer, the results of chemotherapy to date remain unsatisfactory, prompting a need to identify natural agents that could target cancer efficiently with least side effects. Andrographolide (Andro) is one such molecule which has been shown to possess inhibitory effect on cancer cell growth. In this study, Andro, a natural diterpenoid lactone isolated from Andrographis paniculata has been shown to inhibit breast cancer cell proliferation, migration and arrest cell cycle at G2/M phase and induces apoptosis through caspase independent pathway. Our experimental evidences suggest that Andro attenuates endothelial cell motility and tumor-endothelial cell interaction. Moreover, Andro suppresses breast tumor growth in orthotopic NOD/SCID mice model. The anti-tumor activity of Andro in both in vitro and in vivo model was correlated with down regulation of PI3 kinase/Akt activation and inhibition of pro-angiogenic molecules such as OPN and VEGF expressions. Collectively, these results demonstrate that Andro may act as an effective anti-tumor and anti-angiogenic agent for the treatment of breast cancer.     

Formamides mimic aldehydes and inhibit liver alcohol dehydrogenases and ethanol metabolism

Formamides are unreactive analogues of the aldehyde substrates of alcohol dehydrogenases and are useful for structure-function studies and for specific inhibition of alcohol metabolism. They bind to the enzyme-NADH complex and are uncompetitive inhibitors against varied concentrations of alcohol. Fourteen new branched chain and chiral formamides were prepared and tested as inhibitors of purified Class I liver alcohol dehydrogenases: horse (EqADH E), human (HsADH1C*2), and mouse (MmADH1). In general, larger, substituted formamides, such as N-1-ethylheptylformamide, are better inhibitors of HsADH1C*2 and MmADH1 than of EqADH, reflecting a few differences in amino acid residues that change the sizes of the active sites. In contrast, the linear, alkyl (n-propyl and n-butyl) formamides are better inhibitors of EqADH and MmADH1 than of HsADH1C*2, probably because water disrupts van der Waals interactions. These enzymes are also inhibited strongly by sulfoxides and 4-substituted pyrazoles. The structure of EqADH complexed with NADH and (R)-N-1-methylhexylformamide was determined by x-ray crystallography at 1.6 A resolution. The structure resembles the expected Michaelis complex with NADH and aldehyde, and shows for the first time that the reduced nicotinamide ring of NADH is puckered, as predicted for the transition state for hydride transfer. Metabolism of ethanol in mice was inhibited by several formamides. The data were fitted with kinetic simulation to a mechanism that describes the non-linear progress curves and yields estimates of the in vivo inhibition constants and the rate constants for elimination of inhibitors. Some small formamides, such as N-isopropylformamide, may be useful inhibitors in vivo.     

Estrogen receptor activation in response to Azadirachtin A stimulates osteoblast differentiation and bone formation in mice

The positive effects of the sex hormone in sustaining bone homeostasis are exercised by maintaining the equilibrium between cell activity and apoptosis. In this regard, the importance of estrogen receptors in maintaining the bone is that it is an attractive drug target, if devoid of known side effects . In this study, we show that a natural pure compound Azadirachtin A (Aza A) isolated from Azadirachta indica binds selectively to a site in the estrogen receptor, identifying itself to be a selective tissue modifier. Using computational and medicinal chemistry, we show that Aza A binds potentially and selectively to estrogen receptor-α (ERα) as compared with ERβ. This preferential binding of Aza A to ERα with good pharmacokinetic distribution in the body forms metabolites, showing that it is well absorbed. In in vivo estrogen deficiency models for osteoporosis, Aza A at a much lower dose enhances new bone formation at both sites of the trabecular and cortical bone with increased bone strength and presents with no hyperplastic effect in the uterus.