Saccharomyces cerevisiae synthesis

For preparative purposes fermenting baker s yeast (Saccharomyces cerevisiae) is commonly used instead of a purified enzyme preparation. However, isolated pyruvate decarboxylates can also be used30. In this context, the most important substrate is benzaldehyde31 which is converted by n-glucosc fermenting yeast to (7 )-l-hydroxy-l-phenyl-2-propanone. This conversion has gained considerable industrial importance because ( )-l-hydroxy-1-phenyl-2-propanonc is an important precursor for the synthesis of (-)-cphedrin. 

A molecular variation of plasma membrane has been reported by Puccia et al. Reduction of total lipids (XL) content and significant variations of triglyceride (TG) and phospholipids (PL) fractions were observed as a consequence of exposure of C. intestinalis ovaries to TBTCl solutions. In particular, an evident TG decrease and a PL increase were observed, which probably provoked an increment in membrane fluidity, because of the high concentration of long chain fatty acids and, as a consequence, PL. This could be a cell-adaptive standing mechanism toward the pollutants, as observed in Saccharomyces cerevisiae. Also the increase in the content of the polyunsaturated fatty acids (PUPA), important in the synthesis of compounds such as prostaglandin which are present in the ovary in a stress situation, was probably a consequence of a defense mechanism to the stress provoked by the presence of TBTCl. 

Until 1987, the (R)-PaHNL from almonds was the only HNL used as catalyst in the enantioselective preparation of cyanohydrins. Therefore, it was of great interest to get access to HNLs which catalyze the formation of (5 )-cyanohydrins. (5 )-SbHNL [EC 4.1.2.11], isolated from Sorghum bicolor, was the first HNL used for the preparation of (5 )-cyanohydrins. Since the substrate range of SbHNL is limited to aromatic and heteroaromatic aldehydes as substrates, other enzymes with (5 )-cyanoglycosides have been investigated as catalysts for the synthesis of (5 )-cyanohydrins. The (5 )-HNLs from cassava (Manihot esculenta, MeHNL) and from Hevea brasiliensis (HbHNL) proved to be highly promising candidates for the preparation of (5 )-cyanohydrins. Both MeHNL and HbHNL have been overexpressed successfully in Escherichia coli, Saccharomyces cerevisiae and Pichia pastoris. 

Feedback inhibition of amino acid transporters by amino acids synthesized by the cells might be responsible for the well known fact that blocking protein synthesis by cycloheximide in Saccharomyces cerevisiae inhibits the uptake of most amino acids [56]. Indeed, under these conditions, endogenous amino acids continue to accumulate. This situation, which precludes studying amino acid transport in yeast in the presence of inhibitors of protein synthesis, is very different from that observed in bacteria, where amino acid uptake is commonly measured in the presence of chloramphenicol in order to isolate the uptake process from further metabolism of accumulated substances. In yeast, when nitrogen starvation rather than cycloheximide is used to block protein synthesis, this leads to very high uptake activity. This fact supports the feedback inhibition interpretation of the observed cycloheximide effect. 

To study the specific regulation of the synthesis of NCR-sensitive amino acid transporters, Saccharomyces cerevisiae cells are grown with proline or urea as the sole source of nitrogen, i.e., in the absence of NCR (see section 6.3). 

Farhi, M., Dudareva, N., Masci, T. et al. (2006) Synthesis of the food flavoring methyl benzoate by genetically engineered Saccharomyces cerevisiae. Journal of Biotechnology, 122, 307-315. 

Several catalysts are used in the field of microbial reductions. The common features of these catalysts are the high selectivity and their use only on a laboratorial scale. They are applied, for example, in the stereoselective synthesis of pharmaceutical intermediates. The reductions are exclusively selective either in the hydrogenation of the C=C double bond or in that of other reducible groups. One of the most widely used catalysts is baker s yeast. In the following hydrogenations, which are catalyzed by Saccharomyces cerevisiae, high enantioselectivities were achieved (equations 35-38)105-108. 

Chatonnet, P. et al., Synthesis of volatile phenols by Saccharomyces cerevisiae in wines. J. Sci. Food Agric. 62, 191, 1993. 

Bacillus subtilis H17 rec MA5 recT, DNA damage assay Saccharomyces cerevisiae JDl, gene conversion Drosophila melanogaster, sex-linked recessive lethal mutation Unscheduled DNA synthesis, primary rat hepatocytes in vitro Sister chromatid exchange, Chinese hamster ovary CHO cells in vitro... 

Frataxin is another protein which was shown to be targeted into hydrogenosomes (Dolezal et al. 2007). Importantly, I vaginalis frataxin can, in part, functionally replace mitochondrial frataxin, as demonstrated by its ability to partially restore defects in FeS cluster assembly in Saccharomyces cerevisiae Ayfhl mutants and frataxin-deficient Trypanosoma brucei (our unpublished data). In yeast, I vaginalis frataxin also partially restored defects in heme synthesis, although neither heme-containing proteins nor components involved in heme synthesis have been identified in T. vaginalis (Dolezal et al. 2007). 

Yurkevich and his colleagues presented evidence of some novel controls on the synthesis and secretion of /3-D-fructofuranosidase by strains of Saccharomyces cerevisiae. Addition of D-mannitol to give a concentration of 0.5 M in the medium increased the concentration of /3-D-fructofuranosidase in Saccharomyces (globosus) cerevisiae. Similar results were obtained with D-glucitol and D-xylose. As this increase was inhibited by 36 pM cycloheximide, Yurkevich and Khamani168 concluded that a change to a hypertonic medium caused an increase in de novo biosynthesis of /3-D-fructofuranosidase. 

There is conflicting evidence concerning the mutagenicity of 1,2-dimethylhydrazine to bacteria. In a single study, it induced recombination in Saccharomyces cerevisiae. In vitro, 1,2-dimcthylhydrazine formed DNA adducts in human bronchial cells, provoked unscheduled DNA synthesis in rat hepatocytes and induced gene mutation in mammalian cells. It gave positive results in rodents in microbial host-mediated assays. 

Chlorodifluoromethane is mutagenic to Salmonella typhimurium but it did not induce either mutation or gene conversion in Saccharomyces cerevisiae. Chlorodifluoromethane did not induce mutations at the hprt locus or imscheduled DNA synthesis in mammalian cell lines in the presence or absence of an exogenous metabolic activation system. In vivo, it did not induce chromosomal aberrations in bone-marrow cells or dominant lethal effects (lARC, 1987b). These conclusions are supported by a more recent review (WHO, 1991). 

T. G. Mayer, Bemd Kratzer, and R. R. Schmidt, Synthese eines GPI-Ankers der Hefe (Sac charomyces cerevisiae), Angew. Chem. 106 2289 (1994). Synthesis of a GP1 anchor of yeast (Saccharomyces cerevisiae), Angew. Chem. Ini. Ed Engl. 33 2177 (1994). Thomas G. Mayer, Dissertation, Universitat Konstanz, 1995, submitted. 

---