Yeast enzyme

Diacetyl, acetoin, and diketones form during fermentation. Diacetyl has a pronounced effect on flavor, with a threshold of perception of 0.1—0.2 ppm at 0.45 ppm it produces a cheesy flavor. U.S. lager beer has a very mild flavor and generally has lower concentrations of diacetyl than ale. Diacetyl probably forms from the decarboxylation of a-ethyl acetolactate to acetoin and consequent oxidation of acetoin to diacetyl. The yeast enzyme diacetyl reductase can kreversibly reduce diacetyl to acetoin. Aldehyde concentrations are usually 10—20 ppm. Thek effects on flavor must be minor, since the perception threshold is about 25 ppm. 

Riboflavin was first isolated from whey in 1879 by Blyth, and the structure was determined by Kuhn and coworkers in 1933. For the structure determination, this group isolated 30 mg of pure riboflavin from the whites of about 10,000 eggs. The discovery of the actions of riboflavin in biological systems arose from the work of Otto Warburg in Germany and Hugo Theorell in Sweden, both of whom identified yellow substances bound to a yeast enzyme involved in the oxidation of pyridine nucleotides. Theorell showed that riboflavin 5 -phosphate was the source of the yellow color in this old yellow enzyme. By 1938, Warburg had identified FAD, the second common form of riboflavin, as the coenzyme in D-amino acid oxidase, another yellow protein. Riboflavin deficiencies are not at all common. Humans require only about 2 mg per day, and the vitamin is prevalent in many foods. This vitamin... 

Flp/FRT is a system analogous to the cre/loxP system. Flp is an yeast enzyme that recognizes FRT sites. If two FRT sites have a parallel orientation, the DNA segment between these sites will be deleted by the action of the Flp recombinase. 

The enzyme is available from yeast and spinach leaves in quantity. Yeast enzyme is commercially available. TKase gene of many organisms... 

Stewart, J.D., Rodriguez, S. and Kayser, M.M. (2001) Cloning, structure, and activity of ketone reductases from baker s yeast. Enzyme Technologies for Pharmaceutical and Biotechnological, Applications 175-207. 

The yeast-mediated enzymatic biodegradation of azo dyes can be accomplished either by reductive reactions or by oxidative reactions. In general, reductive reactions led to cleavage of azo dyes into aromatic amines, which are further mineralized by yeasts. Enzymes putatively involved in this process are NADH-dependent reductases [24] and an azoreductase [16], which is dependent on the extracellular activity of a component of the plasma membrane redox system, identified as a ferric reductase [19]. Recently, significant increase in the activities of NADH-dependent reductase and azoreductase was observed in the cells of Trichosporon beigelii obtained at the end of the decolorization process [25]. 

Yeast Enzymes. Yeast has a special relationship with enzymes as enzymes were first discovered in yeast. The name enzyme is derived from the German for in yeast (i.e. Zym). It was found that an extract produced from the yeast could undertake a fermentation. This at the time was a philosophically important point since it showed that there... 

Larsen, T.M., Wedeking, J.E., Rayment, I. and Reed, G.H. (1996) A carboxylate oxygen of the substrate bridges the magnesium ions at the active site of enolase structure of the yeast enzyme complexed with the equilibrium mixture of 2-phosphoglycerate and phosphoenolpyruvate at 1.8 A resolution, Biochemistry, 30, 4349-4358. 

The recent work on the stereospecificity of hydroxymethylglutaryl-CoA reductase 71 76> is particularly interesting. The reaction catalyzed by this enzyme is an important early step in the synthesis of terpenoids and steroids. The yeast enzyme and the liver enzyme both have the same stereospecificities. The overall reaction catalyzed is the reduction of hydroxymethylglutaryl CoA to mevalonic acid, as shown in scheme 1. Two molecules of NADPH are used to reduce the Co-A-bound carboxyl... 

The books, however, cannot yet be closed. Although the flexibilities of the yeast enzyme at 25 °C and thermophilic enzyme at 65 °C are similar, and although both show unmistakeable evidence of tunneling, the nature of the tunneling process appears to be different. This is another instance in which the temperature dependences of the isotope effects generate a complex and ill-understood picture. 

Yeast H2A has the PI-3 kinase motif found in mammalian H2AX. This motif is important for yeast to repair DSBs and in non-homologous end joining. The yeast enzyme catalyzing phosphorylation of yeast H2AX at Ser-129 (homologous to serine 139 of mammalian H2AX) is Mecl [100] (Fig. 8). 

This enzyme [EC 2.7.1.30], also known as glycerokinase and ATPiglycerol 3-phosphotransferase, catalyzes the reaction of ATP with glycerol to produce ADP and glycerol 3-phosphate. Both glycerone (or, dihydroxyacetone) and L-glyceraldehyde can serve as substrates. The nucleoside triphosphate can be substituted by UTP and, in the case of the yeast enzyme, ITP and GTP. 

Haldane is also valid for the ordered Bi Bi Theorell-Chance mechanism and the rapid equilibrium random Bi Bi mechanism. The reverse reaction of the yeast enzyme is easily studied an observation not true for the brain enzyme, even though both enzymes catalyze the exact same reaction. A crucial difference between the two enzymes is the dissociation constant (i iq) for Q (in this case, glucose 6-phosphate). For the yeast enzyme, this value is about 5 mM whereas for the brain enzyme the value is 1 tM. Hence, in order for Keq to remain constant (and assuming Kp, and are all approximately the same for both enzymes) the Hmax,f/f max,r ratio for the brain enzyme must be considerably larger than the corresponding ratio for the yeast enzyme. In fact, the differences between the two ratios is more than a thousandfold. Hence, the Haldane relationship helps to explain how one enzyme appears to be more kmeticaUy reversible than another catalyzing the same reaction. 

This enzyme [EC 1.1.1.3] catalyzes the reaction of homoserine with NAD(P) to produce aspartate 4-semialdehyde and NAD(P)H. NAD is the better of the two coenzymes with the yeast enzyme whereas NADP+ is preferred by the Neurospora enzyme. See also Aspartate Kinase... 

Cetylpyridinium chloride (CPC)/ hexane a-Amylase from brewers yeast and invertase from bakers yeast Enzyme activities in cells entrapped in RMs were high compared to free cells [284]... 

Uridine 5 -(/3-D-glucopyranosyl pyrophosphate)390 and the phos-phonate derivative310 67 do not undergo epimerization with the yeast enzyme. 

Phosphorolysis of the glycosyl esters of sugar nucleotides leads to the corresponding nucleoside 5 -pyrophosphate and glycosyl phosphate. A wheat-germ enzyme specific for adenosine 5 -(a-D-glucopy-ranosyl pyrophosphate),462 and a yeast enzyme specific for guanosine 5 -(a-D-mannopyranosyl pyrophosphate),463,464 are known. 

For synthetic purposes the E. coli transketolase has a certain advantage over the enzymes from spinach and yeast, because the conversion of a-hydroxypyru-vate with a rate of 60 U (mg of protein) [6b] is significantly higher than the rates of 2 U mg" and 9 U mg reported for the spinach and yeast enzymes [9, 11],... 

Additional information <1, 7-9, 12-17, 21> (<7> inhibitory effect of phosphonate analogues of 1,3-diphosphoglycerate, overview [49] <21> no effect by glucose 6-phosphate, fructose 6-phosphate, fructose 1,6-phosphate, pyruvate, phosphoenolpyruvate and lactate [70] <13> double-inhibition studies, kinetics, modeling of inhibitor binding, e.g. phosphate [55] <13> enzyme is regulated by multivalent anions, overview [55] <8> no inhibition by Hg [25] <1,7,9,12-17> yeast enzyme is insensitive to thiol reagents [17]) [17, 25, 49, 55, 70]... 

The amino-acid sequence has been determined for the SOD of four species (Table 2). There are minor differences for the yeast enzyme Asn-55 and Asn-92 against Asp-55 and Asp-92 and for the human enzyme concerning the amidation of six residues and Ser-17 and Val-98 against He-17 and Ser-98 . Characteristic is the very low amount or the absence of methionine and tryptophan. There is no methionine in human SOD, the yeast SOD contains only Met-84, the bovine SOD Met-115, and the equine SOD Met-99 and Met-117. Tryptophan is absent with the exception of Trp-32 in human SOD. 

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