Glycerol In Absence Research Articles

CaZF, a Plant Transcription Factor Functions through and Parallel to HOG and Calcineurin Pathways in Saccharomyces cerevisiae to Provide Osmotolerance

Salt-sensitive yeast mutants were deployed to characterize a gene encoding a C2H2 zinc finger protein (CaZF) that is differentially expressed in a drought-tolerant variety of chickpea (Cicer arietinum) and provides salinity-tolerance in transgenic tobacco. In Saccharomyces cerevisiae most of the cellular responses to hyper-osmotic stress is regulated by two interconnected pathways involving high osmolarity glycerol mitogen-activated protein kinase (Hog1p) and Calcineurin (CAN), a Ca2+/calmodulin-regulated protein phosphatase 2B. In this study, we report that heterologous expression of CaZF provides osmotolerance in S. cerevisiae through Hog1p and Calcineurin dependent as well as independent pathways. CaZF partially suppresses salt-hypersensitive phenotypes of hog1, can and hog1can mutants and in conjunction, stimulates HOG and CAN pathway genes with subsequent accumulation of glycerol in absence of Hog1p and CAN. CaZF directly binds to stress response element (STRE) to activate STRE-containing promoter in yeast. Transactivation and salt tolerance assays of CaZF deletion mutants showed that other than the transactivation domain a C-terminal domain composed of acidic and basic amino acids is also required for its function. Altogether, results from this study suggests that CaZF is a potential plant salt-tolerance determinant and also provide evidence that in budding yeast expression of HOG and CAN pathway genes can be stimulated in absence of their regulatory enzymes to provide osmotolerance.

NADP-glutamate dehydrogenase from the halophilic archaeon Haloferax mediterraner. enzyme purification, N-terminal sequence and stability

An NADP(H)-specific glutamate dehydrogenase of Haloferax mediterranei has been purified to apparent homogeneity and characterised. The purified enzyme was stabilized by glycerol in absence of salt. Glutamate dehydrogenase from Hf. mediterranei is a hexameric enzyme with a native molecular mass of 320 kDa composed of monomers each with a molecular mass of 55 kDa. At pH 8.5 the enzyme has K ms of 0.018, 0.34 and 4.2 mM for NADP+, 2-oxoglutarate and ammonium, respectively. Amino acid composition and sequence of the first 16 residues of the N-terminus have been determined.

NADP-glutamate dehydrogenase from the halophilic archaeon Haloferax mediterranei: enzyme purification, N-terminal sequence and stability.

An NADP(H)-specific glutamate dehydrogenase of Haloferax mediterranei has been purified to apparent homogeneity and characterised. The purified enzyme was stabilized by glycerol in absence of salt. Glutamate dehydrogenase from Hf. mediterranei is a hexameric enzyme with a native molecular mass of 320 kDa composed of monomers each with a molecular mass of 55 kDa. At pH 8.5 the enzyme has Kms of 0.018, 0.34 and 4.2 mM for NADP+, 2-oxoglutarate and ammonium, respectively. Amino acid composition and sequence of the first 16 residues of the N-terminus have been determined.

STUDIES ON REACTIONS RELATING TO CARBOHYDRATES AND POLYSACCHARIDES: LII. THE PREPARATION, SEPARATION AND IDENTIFICATION OF THE ISOMERIC PROPYLIDENE, ISOBUTYLIDENE, t-AMYLIDENE AND DIBROMOETHYLIDENE GLYCEROLS AND THE GENERAL PROPERTIES OF GLYCEROL CYCLIC ACETALS

The condensation of propionaldehyde, isobutyraldehyde, trimethylacetaldehyde and dibromoacetaldehyde with glycerol has been carried out in the presence of a catalyst (40% sulphuric acid) at 90 °C., and the resulting products have been shown to consist in each case of a mixture of the five- and six-membered cyclic acetals. The separation of these isomers from the acetal mixture was rendered possible by the difference in the physical properties of their benzoates. The structure of the latter was proved by saponification, methylation, hydrolysis and isolation of the resulting glycerol α- and glycerol β-methyl ethers respectively.With the isomers from dibromoacetaldehyde this method could not be used, owing to the labile character of the bromine atoms in presence of alkali. Their structures were proved by direct synthesis of the five-membered acetal benzoate from glycerol α-benzoate and dibromoacetaldehyde.The data obtained provide additional evidence of the marked influence exerted by the polar character of the aldehyde on the extent and character of acetal condensation. Increase in the electronegative character increases the amount formed of the five-membered acetal and decreases that of the six-membered. Trimethylacetaldehyde condensed readily with glycerol in absence of a catalyst. Lowering of temperature, in presence of the catalyst, favored the formation of the six-membered acetals, in agreement with the earlier work of van Roon. The results further confirm the Hibbert-Michael Ring Partition Principle.A general comparison is made of the physical properties of the ethylidene–, propylidene–, isobutylidene–, t–amylidene–, bromoethylidene–, and dibromoethylidene glycerol acetals.By substituting diphenylamine for aniline in the synthesis of trimethylacetaldehyde from trimethylpyruvic acid the yield is increased from 25 to 40%.