Yeast reverse

Mehta, R.D. von Borstel, R.C. (1981) Mutagenic activity of 42 encoded compounds in the haploid yeast reversion assay, strain XV185-14C. In de Serres, F.J. Ashby, J., eds, Progress in Mutation Research, Vol. 1, Evaluation of Short-Term Tests for Carcinogens. Report of the International Collaborative Program, Amsterdam, Elsevier/North-Holland. pp. 414 423... 

S. typhimurium TA102, TA2638 Eukaryotic organisms Yeasts Reverse mutations No data + Watanabe et al. 1998a Chromium trioxide, sodium dichromate... 

Electroporation. When bacteria are exposed to an electric field a number of physical and biochemical changes occur. The bacterial membrane becomes polarized at low electric field. When the membrane potential reaches a critical value of 200—300 mV, areas of reversible local disorganization and transient breakdown occur resulting in a permeable membrane. This results in both molecular influx and efflux. The nature of the membrane disturbance is not clearly understood but bacteria, yeast, and fungi are capable of DNA uptake (see Yeasts). This method, called electroporation, has been used to transform a variety of bacterial and yeast strains that are recalcitrant to other methods (2). Apparatus for electroporation is commercially available, and constant improvements in the design are being made. 

Candida utilis is grown on sulfite waste Hquor in Western Europe and North America, on sugar cane molasses in Cuba and Taiwan and on ceUulose acid hydrolysates in Eastern Europe and the former Soviet Union. C. ///i/if utilizes hexoses, pentoses, and many organic acids. Sulfite Hquor from hardwoods contains 2—3% fermentable sugars of which 20% are hexoses and 80% pentoses in softwood Hquors the proportions are reversed. The SO2 must be stripped out to allow yeast growth, which is carried out in large, highly-aerated fermentors. Eor continuous fermentations, carried out at pH 4 and 30°C, the dilution rate is 0.27—0.30 (34). 

Fig. 17.6. Experimental configuration for the integrated, primary purification of intracellular proteins from unclarified disruptates. Panel A configuration employed for the purification of G3PDH from baker s yeast. Elution was performed in packed bed mode under reversed flow. Panel B configuration for loading, wash and elution in fluidised bed mode (employed for the purification of L-asparaginase from Erwinia chrysanthemi).

Endosulfan is toxic to yeast but is also mutagenic without activation (Yadav et al. 1982). In vitro, endosulfan induced reverse mutations and mitotic gene conversion and increased the percentage of aberrant colonies in Saccharomyces cerevisiae but did not induce mitotic cross-overs (Yadav et al. 1982). 

A solution to the problem of introns is to isolate mRNA extracted from the human pancreas cells that make insulin. These cells are rich in insulin mRNA from which introns have already been spliced out. Using the enzyme reverse transcriptase it is possible to convert this spliced mRNA into a DNA copy. This copy DNA (cDNA), which carries the uninterrupted genetic information for insulin can be cloned. Although yeast cells (Saccharomyces) can splice out introns it is normal practice to eliminate them anyway by cDNA cloning. 

Indirect evidence of the reversal of enzymic synthesis of levan has recently been obtained.10Ba Enzyme preparations from B. subtilis were shown to contain an enzyme capable of hydrolyzing levan (in addition to the levan-synthesizing enzyme) in a system composed of D-glucose, levan, yeast invertase (to hydrolyze sucrose formed) and the B. subtilis enzyme preparation. 

The above observations suggested that hexoses arise in Nature by reaction of glycerose with dihydroxyacetone. A vast amount of practical information has been derived from investigation of plant- and muscle-extracts, two dissimilar systems that show many similarities in their biosynthetic manipulations. There is a close parallelism in the sequence of intermediates involved in the processes wherein D-glucose is converted to ethanol and carbon dioxide by yeasts, and to lactic acid by muscle during contraction. The importance of these schemes lies in their reversibility, which provides a means of biosynthesis from small molecules. 

I, 7-diphosphate.170 1 (f> This tetrose phosphate is involved with phosphoenol pyruvate in the formation of shikimic acid via 3-deoxy-2-keto-D-ara6ino-heptonic acid 7-phosphate and, hence, of aromatic compounds.170(d) A synthesis of the tetrose phosphate has been described.170 1 Aldolase shows a high affinity for the heptulose diphosphate and, compared with that for D-fructose 1,6-diphosphate, the rate of reaction is about 60 %. The enzyme transaldolase, purified 400-fold from yeast, catalyzes the following reversible reaction by transfer of the dihydroxyacetonyl group.l70(o>... 

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