Dehydrogenases benzaldehyde dehydrogenase

This pathway is supported by the demonstration of benzyl alcohol dehydrogenase, benzaldehyde dehydrogenase, benzoyl-CoA ligase, and benzoyl-CoA reductase activities in cell extracts (Biegert and Fuchs 1995). The benzyl alcohol dehydrogenase from benzyl alcohol-grown cells was similar in many of its properties to those from the aerobic bacteria Acinetobacter calcoaceticus and Pseudomonas putida (Biegert et al. 1995). 

Confirmation of this proposed pathway was established by Altenschmidt Fuchs (1991, 1992) in their study of the biochemistry of toluene decay by the denitrifying Pseudomonas sp. strain K172. These investigators confirmed the presence of benzyl alcohol dehydrogenase, benzaldehyde dehydrogenase, and benzoyl-CoA synthetase in cell-free extracts of this isolate. Further, [14C]benzyl... 

Other approaches could use transcriptional regulators that directly bind the substrate or product of the reaction and activate the reporter gene. For instance, a mutant transcriptional activator from Pseudomonas putida, NahH, was used that can bind various benzoic acids to develop a screening/selection method to detect the action of benzaldehyde dehydrogenase [45]. A transcriptional regulator may need to be engineered to bind the desired compound before it can be used in such a manner [46]. 

Benzyl alcohol can be produced from benzaldehyde (S) by a dehydrogenation reaction catalyzed by yeast alcohol dehydrogenase (YADH). Nikolova et al. (1995) obtained initial-rate data for this reaction using immobilized YADH immersed in iso-octane with 1% v/v water. The following data were obtained ... 

Deviations from equation (57) have also been used to demonstrate that tunnelling is important in the enzyme-catalysed oxidation of benzyl alcohol to benzaldehyde by NAD+ and yeast alcohol dehydrogenase (YADH) (reaction (60)) (Cha et al., 1989 Klinman, 1991). 

Table 40 The primary and secondary deuterium-tritium and hydrogen-tritium KIEs for the oxidation of benzyl alcohol to benzaldehyde with NAD+ and yeast alcohol dehydrogenase at 25°C.a...

Yeast alcohol dehydrogenase, catalysis of oxidation by NAD of benzyl alcohol equilibrium interconversion of benzyl alcohol and benzaldehyde... 

A few years later, Cha, Murray and Klinman published a report on isotope effects in the redox interconversion of benzyl alcohol-benzaldehyde/NAD -NADH, with catalysis by yeast alcohol dehydrogenase. This article effected among biochemists... 

Fig. 6 Illustration from Chin and Klinman. Increased catalytic activity of horse-liver alcohol dehydrogenase in the oxidation of benzyl alcohol to benzaldehyde by NAD, measured by cat/ M (ordinate), correlates with the Swain-Schaad exponent for the -secondary isotope effect (abscissa), for which values above about four are indicators of tunneling. This is a direct test of the hypothesis that tunneling in the action of this enzyme contributes to catalysis. As the rate increases by over two orders of magnitude and then levels off, the anomalous Swain-Schaad exponents also increase and then level off. Reproduced from Ref. 28 with the permission of the American Chemical Society.

Isotope effects have also been applied extensively to studies of NAD+/NADP+-linked dehydrogenases. We typically treat these enzymes as systems whose catalytic rates are limited by product release. Nonetheless, Palm clearly demonstrated a primary tritium kinetic isotope effect on lactate dehydrogenase catalysis, a finding that indicated that the hydride transfer step is rate-contributing. Plapp s laboratory later demonstrated that liver alcohol dehydrogenase has an intrinsic /ch//cd isotope effect of 5.2 with ethanol and an intrinsic /ch//cd isotope effect of 3-6-4.3 with benzyl alcohol. Moreover, Klin-man reported the following intrinsic isotope effects in the reduction of p-substituted benzaldehydes by yeast alcohol dehydrogenase kn/ko for p-Br-benzaldehyde = 3.5 kulki) for p-Cl-benzaldehyde = 3.3 kulk for p-H-benzaldehyde = 3.0 kulk for p-CHs-benzaldehyde = 5.4 and kn/ko for p-CHsO-benzaldehyde = 3.4. 

Human polymorphisms in several enzymes involved in toluene metabolism are known. In Mongoloid populations, deficiency in the low form of aldehyde dehydrogenase H2 (ALDH2) is common approximately half of the Japanese population lacks this enzyme. In ALDH2-deficient exposed workers, an increased level of benzyl alcohol was found, but benzaldehyde was not detectable urinary excretion of hippurate was decreased in the deficient individuals. The CYPlAl polymorphism, alcohol consumption and smoking were all associated with decreased hippurate excretion, but the interdependence was too complex to allow detailed conclusions on the mechanisms to be drawn (Kawamoto et al., 1995). 

One step or two-step transfer Another major question about dehydrogenases is whether the hydrogen atom that is transferred moves as a hydride ion, as is generally accepted, or as a hydrogen atom with separate transfer of an electron and with an intermediate NAD or NADPH free radical. In one study para-substituted benzaldehydes were reduced with NADH and NAD2H using yeast alcohol dehydrogenase as a catalyst.30 This permitted the application of the Hammett equation (Box 6-C) to the rate data. For a series of benzaldehydes for which o+ varied widely, a value... 

Enzymatic processes also advance in the area of large-scale pharma intermediates /flactam antibiotics can now be produced in a fully biotechnological process, including the semi-synthesis from the /flactam core to the penicillin or cephalosporin. A precursor to ephedrine, long produced by a whole-cell process in yeast, can be obtained from benzaldehyde and acetaldehyde with the help of pyruvate dehydrogenase acting as a carboligase. 

P. C. Babbitt, J. A. Gerlt, G. L. Kenyon, Identification and characterization of a mandelamide hydrolase and an NAD(P)+-dependent benzaldehyde dehydrogenase from Pseudomonas putida ATCC 12633,... 

During the biotransformation of benzaldehyde by fermenting yeast (Scheme 1) to (R)-PAC the reduction of the benzaldehyde to benzyl alcohol is a serious problem, caused partially by the presence of alcohol dehydrogenases... 

Benzaldehyde dehydrogenase (BDH), a hypothetical enzyme, catalyzes the oxidation of benzaldehyde to benzoic acid. The enzyme has a flavin prosthetic group that accepts electrons from the substrate upon oxidation ... 

Similarly, (S)-phenylmethanol (benzyl alcohol, 29) is produced exclusively by reduction of deuteriated benzaldehyde 28 by the liver alcohol dehydrogenase-NAD+ reduction system. 

Benzaldehyde Benzyl alcohol Alcohol dehydrogenase Almond... 

The difference between primary and secondary kinetic effects can be elucidated by using the oxidation of benzyl alcohol by nicotinamide adenine dinucleotide (NAD+) as an example (Scheme 10.1 (A)). This reaction is catalyzed by alcohol dehydrogenase (ADH), and has been extensively studied [10, 21-27]. In this reaction, the hydrogen at position is transferred from benzyl alcohol to NAD+, forming benzaldehyde and reduced nicotinamide (NADH), making the primary position. Conversely, is retained upon reaction, making this the secondary position. 

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