Enzymatic oxidation, ethanol acetaldehyde

In a further study continuous electrolytic oxidation of ethanol was performed with the molecular-interfaced ADH/MB/NAD. The electrode potential was controlled at 0.35 V vs. Ag/AgCl. Ethanol in a solution was enzymatically oxidized to acetaldehyde with resulting in the reduction of NAD to NADH. The turnover number of the NAD/NADH cycle was calculated from the total conversion of ethanol and the coulomb during the electrolysis. The results clearly showed that NAD was electrochemically regenerated within the polypyrrole membrane through the electron transfer from ADH, NAD and MB to the electrode. 

Ru(bpy)3" ]. This reduced species is oxidized by Rh(bpysa).r, resulting in the formation of the reduced hydridorhodium complex, which provides further reduction of NAD" ". The NADH regenerated in this photochemical system was coupled with the enzymatic reduction of acetaldehyde to ethanol in the presence of alcohol dehydrogenase. 

To measure ethanol in blood, enzymatic analysis is the method of choice for many laboratories. In this method, ethanol is measured by oxidation to acetaldehyde with NAD, a reaction catalyzed by alcohol dehydrogenase (ADH). With this reaction, formation of NADH, measured at 340nm, is proportional to the amount of ethanol in the specimen. The reaction is driven almost completely to the right by use of excess NAD and ADH and agents such as semicarbazide or tris (hydroxymethyl) aminomethane to trap acetaldehyde as it is formed. ... 

Fig, 3,8 Enzymatic oxidation of ethanol to acetaldehyde [40]. ADH = alcohol dehydrogenase, NAD+ and FMN = cofactors, catalase = second enzyme to regenerate cofactors... 

Figure 4. Enzymatic oxidation of ethanol to acetaldehyde according to U.S. Patent 4 481 292.

The alcohol in a distillate can be estimated from its specific gravity or refractive index or more occasionally by chemical or enzymatic analysis. These last methods are more sensitive and are usually reserved for measuring small quantities of ethanol. For example, the alcohol in blood may be estimated by microdiffusion into a dilute acidified solution of potassium dichromate where it is oxidized to acetaldehyde while the orange-red dichromate is reduced to a green chromous salt ... 

Acetaldehyde is mostly formed by the enzymatic oxidation of ethanol, the latter is formed in roots under anoxic conditions or in anoxic stems of woody plants [13]. Large fluxes of acetaldehyde have been observed from the leaves when roots are flooded (limited access to oxygen) or exposed to anoxia. It has also recently been discovered that acetaldehyde can arise in leaves directly from metabolism that occurs during light-dark transitions [14]. 

Do optically active 1-methyl-TIQs, as sketched in Fig. 32 for the synthesis of (7 )-salsolinol, originate from a Pictet-Spengler reaction of dopamine with acetaldehyde derive from ethanol, or are they the result of a Pictet-Spengler reaction of biogenic amines with pyruvic acid, as sketched in Fig. 33 Based on the accumulated data it seems reasonable to propose that optically active TIQs are formed by the pyruvic acid pathway, and that the pyruvic acids may be derived from an impaired glucose metabolism or an impaired amino acid metabolism. Whether the intermediate TIQ-1-carboxylic acids 91a,b are enzymatically decarboxylated to afford 64a,b in a different enantiomeric ratio, or whether optically active TIQs are formed by oxidative decarboxylation of TIQ 91 to DIQ 120, followed by an asymmetric reduction, remains open to question. 

The 3-carbamidopyridinium ring is the chemically active portion of the enzymatic cofactors, NAD and NADP (nicotinamide adenine dinucleotide and its phosphate). A typical reaction involving NAD is the stereospecific (with respect to both cofactor and substrate) oxidation of ethanol to acetaldehyde catalyzed by the enzyme, alcohol dehydrogenase (Eq. 33). 

Enzyme Cofactors- In many enzymatic reactions, and in particular biological reactions, a second substrate (i.e., species) must be introduced to activate the enzyme. This substrate, which is referred to as a cofactor or coenzyme even though it is not an enzyme as such, attaches to the enzyme and is most often either reduced or oxidized during the course of die reaction. The enzyme-cofactor complex is referred to as a holoenzyme. The inactive form of the enzyme-cofactor complex for a specific reaction and reaction direction is called an apoenzyme. An example of the type of system in which a cofactor is used is the formation of ethanol from acetaldehyde in the presence of the enzyme alcohol dehydrogenase (ADH) and the cofactor nicotinamide adenine dinuoleotide (NAD) ... 

Although comparatively well absorbed (30-55%), the oral efficacy of ampicillin for systemic infections can be enhanced significantly through the preparation of pro-drugs. In contrast to ampicillin itself, which is amphoteric, bacampicillin is a weak base and is very well absorbed in the duodenum (80-98%). Enzymatic ester hydrolysis in the gut wall liberates oarbon dioxide and ethanol, followed by spontaneous loss of aoetaldehyde and production of ampicillin. The acetaldehyde is metabolized oxidatively by alcohol dehydrogenase to produce acetic acid, which joins the normal metabolic pool. 

This colour change is the principle on which the breath analyser operates. Instrumental methods of breath alcohol analysis have recently been reviewed [24]. Enzymatic methods are usually based on alcohol dehydrogenase which catalyses the oxidation of ethanol to acetaldehyde ... 

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