Alcohol Dehydrogenases ADH

Although alcohol dehydrogenases (ADH) also catalyze the oxidation of aldehydes to the corresponding acids, the rate of this reaction is significantly lower. The systems that combine ADH and aldehyde dehydrogenases (EC 1.2.1.5) (AldDH) are much more efficient. For example, HLAD catalyzes the enantioselective oxidation of a number of racemic 1,2-diols to L-a-hydroxy aldehydes which are further converted to L-a-hydroxy acids by AldDH (166). 

ATP D-frnctose-6-phosphate 1-phosphotrans-ferase, and alcohol dehydrogenase (ADH), or alcohol NAD oxidoreduetase, which catalyze the reactions shown here. 

The leading substrate (A) is nicotinamide adenine dinucleotide (NAD ), and NAD and NADH (product Q) compete for a common site on E. A specific example is offered by alcohol dehydrogenase (ADH) ... 

Liver alcohol dehydrogenase (ADH) is relatively nonspecific and will oxidize ethanol or other alcohols, including methanol. Methanol oxidation yields formaldehyde, which is quite toxic, causing, among other things, blindness. Mistaking it for the cheap... 

Ethanol Electrodes The reliable sensing of ethanol is of great significance in various disciplines. The enzymatic reaction of ethanol with the cofactor nicotinamide-adenine dinucleotide (NAD+), in the presence of alcohol dehydrogenase (ADH)... 

Materials. Microspherical PGG glucan (Adjuvax, Alpha-Beta Technology, Worcester, MA) was prepared from Saccharomyces cereviseae strain R4 cells (11). Zymosan, cytochrome c (cyt c), bovine serum albumin (BSA), yeast alcohol dehydrogenase (ADH), Complete Freunds Adjuvant (CFA) and Incomplete Freunds Adjuvant (IFA) were purchased from Sigma Chemical Co. (St. Louis, MO). 

The reduction of several ketones, which were transformed by the wild-type lyophilized cells of Rhodococcus ruber DSM 44541 with moderate stereoselectivity, was reinvestigated employing lyophilized cells of Escherichia coli containing the overexpressed alcohol dehydrogenase (ADH- A ) from Rhodococcus ruber DSM 44541. The recombinant whole-cell biocatalyst significantly increased the activity and enantioselectivity [41]. For example, the enantiomeric excess of (R)-2-chloro-l-phenylethanol increased from 43 to >99%. This study clearly demonstrated the advantages of the recombinant whole cell biocatalysts over the wild-type whole cells. 

The amperometric dehydrogenase sensor for ethanol consists of a platinum electrode on the surface of which alcohol dehydrogenase (ADH), Meldra blue (MB) and NAD are immobilized with a conductive polypyrrole membrane as schematically illustrated in Fig.24. 

Alcohol metabolism (Figure 6.37) occurs mainly through oxidative pathways involving the enzymes alcohol dehydrogenase (ADH), acetaldehyde dehydrogenase (ALDH),... 

Asymmetric electroreduction of ketones to the corresponding chiral alcohols has recently been reported. Typical examples are the reduction of ketones bearing chiral auxiliaries [68, 69], and the indirect reduction of ketones with alcohol dehydrogenase (ADH), as a mediator (Scheme 32) [70]. 

Biocatalysis is still an emerging field hence, some transformations are more established than others.Panke et alP have performed a survey of patent applications in the area of biocatalysis granted between the years 2000 and 2004. They found that although hydrolases, which perform hydrolyses and esterifications, still command widespread attention and remain the most utilized class of enzyme (Figure 1.5), significant focus has turned towards the use of biocatalysts with different activities and in particular alcohol dehydrogenases (ADHs) - also known as ketoreductases (KREDs) - used for asymmetric ketone reduction. 

Most of the alcohol distributes into body water, but like most solvents and anesthetics some distributes into fat. It is excreted in the urine and breath, hence the utility of taking breath samples to evaluate alcohol exposure. The majority of alcohol is metabolized in the liver. Alcohol dehydrogenase (ADH) metabolizes alcohol to acetaldehyde. Acetaldehyde is toxic, with elevated levels causing flushing, headache, nausea, and vomiting. Acetaldehyde is in turn quickly metabolized to the less toxic acetate by acetaldehyde dehydrogenase (ALDH) (Figure 3.1). 

Blanch and coworkers [145] investigated in detail the solubilization properties of a-chymotrypsin and alcohol dehydrogenase (ADH) in RMs prepared by the above three techniques. Protein solubilization in RMs greatly depends on the method used for protein addition as well as on the size of the protein and of the RM. For the dry addition method protein solubilization is strongly dependent on micelle size whereas for the injection method it is less dependent. For smaller proteins like a-chymotrypsin (diameter of 44 A), maximum solubilization occurred when the micelle diameter was 50 - 60 A. For larger proteins like ADH... 

In a first reactor, where benzoylformate decarboxylase (BFD) is retained, benz-aldehyde and acetaldehyde are coupled to yield (S)-hydroxy-l-phenylpropanone. This hydroxy ketone is then reduced to the corresponding diol in a second reactor by an alcohol dehydrogenase (ADH). Regeneration of the necessary cofactor is achieved by formate dehydrogenase (FDH) or by other methods. To avoid additional consumption of redox equivalents by unselective reduction of residual starting material from the first reactor, the volatile aldehydes are removed via an inline stripping module between the two membrane reactors. In this setup the diol was produced with high optical purity (ee, de > 90%) at an overall space-time yield of 32 g L d . ... 

The volatiles produced by the LOX pathway and autoxidation are typically volatile aldehydes and alcohols responsible for fresh and green sensorial notes. In the LOX pathway these volatile compounds are produced in response to stress, during ripening or after damage of the plant tissue. The pathway is illustrated in Scheme 7.2. Precursors of the LOX (EC 1.13.11.12) catalysed reactions are Cis-polyunsaturated fatty acids with a (Z,Z)-l,4-pentadiene moiety such as linoleic and a-linolenic acids that are typically oxidised into 9-, 10- or 13-hydro-peroxides depending on the specificity of the LOX catalyst. These compounds are then cleaved by hydroperoxide lyase (HPL) into mainly C, C9 and Cio aldehydes, which can then be reduced into the corresponding alcohols by alcohol dehydrogenase (ADH EC 1.1.1.1) (Scheme 7.2) [21, 22]. The production of volatile compounds by the LOX pathway depends, however, on the plants as they have different sets of enzymes, pH in the cells, fatty acid composition of cell walls, etc. 

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