Alcohol dehydrogenase nucleotides

Alcohol dehydrogenases catalyze oxidation of alcohols in a reaction dependent on the pyridine nucleotide NAD+ [Eq. (5)]. Since the reaction is reversible, alcohol dehydrogenases also catalyze the reduction of aldehydes by... 

The carbonyl reductases catalyze reduction of aldehydes and ketones by reduced pyridine nucleotides (NADH and/or NADPH). As mentioned earlier, alcohol dehydrogenase can perform this function in the presence of a high ratio of NADH to NAD+. Other enzymes capable of carbonyl reduction include the aldehyde and ketone reductases. The aldehyde and ketone reductases have a ubiquitous species distribution, with the enzymes present in organisms ranging from bacteria to vertebrates. The mammalian carbonyl reductases have been extensively reviewed (101). 

The liver alcohol dehydrogenase mentioned in the preceding section has the same pro-R stereospecificity for NAD and ethanol as yeast alcohol dehydrogenase. Furthermore, the oxidation of ethanol by a microsomal oxidizing system, or by catalase and H2O2, likewise proceeds with pro-R stereospecificity for the ethanol77>. The catalase-H2C>2 system is so very different, however, from the pyridine nucleotide dehydrogenase, that one wonders whether the similarity in stereospecificity for ethanol is fortuitous. 

ALCOHOL DEHYDROGENASE Pyridine nucleotide transhydrogenase, NAD(Pr TRANSHYDROGENASE PYRIDOXAL 4-DEHYDROGENASE PYRIDOXAL KINASE... 

Alcohol dehydrogenase is also obtained from yeast. Yeast alcohol dehydrogenase (YADH) was the first pyridine nucleotide-dependent dehydrogenase to be crystallized by Negelein and Wulff in 1937.1342 YADH is a tetramer of molecular weight 140000-150000. The amount of zinc determined varies,1343 but there are strong indications that the subunits of YADH and LADH have similar structures, including the presence of two zinc atoms. 

Several of the B vitamins function as coenzymes or as precursors of coenzymes some of these have been mentioned previously. Nicotinamide adenine dinucleotide (NAD) which, in conjunction with the enzyme alcohol dehydrogenase, oxidizes ethanol to ethanal (Section 15-6C), also is the oxidant in the citric acid cycle (Section 20-10B). The precursor to NAD is the B vitamin, niacin or nicotinic acid (Section 23-2). Riboflavin (vitamin B2) is a precursor of flavin adenine nucleotide FAD, a coenzyme in redox processes rather like NAD (Section 15-6C). Another example of a coenzyme is pyri-doxal (vitamin B6), mentioned in connection with the deamination and decarboxylation of amino acids (Section 25-5C). Yet another is coenzyme A (CoASH), which is essential for metabolism and biosynthesis (Sections 18-8F, 20-10B, and 30-5A). 

Boyer, P.D. and Theorell, H. The change in reduced diphosphopyridine nucleotide (DPNH) fluorescence upon combination with liver alcohol dehydrogenase (ADH). Acta Chem. Scand., 10 447-450, 1956. 

Scharschmidt M, Fisher MA, Cleland, WW. Variation of transition-state structure as a function of the nucleotide in reactions catalyzed by dehydrogenases. 1. Liver alcohol dehydrogenase with benzyl alcohol and yeast aldehyde dehydrogenase with benzalde-hyde. Biochemistry 1984 23 5471-5478. 

Trcek, J. 2005. Quick identification of acetic acid bacteria based on nucleotide sequences of the 16S-23S rDNA internal transcribed spacer region and of the PQQ-dependent alcohol dehydrogenase gene. Systematic Applied Microbiology 28 735-745. 

The following abbreviations will be used ADH—alcohol dehydrogenase DPN — diphosphopyridine nucleotide DPNH—reduced diphosphopyridine nucleotide OP—1,10-phenanthroline 8-OHQ—8-hydroxyquinoline a,a -D—a,a -dipyridyl 8-OHQ5SA—8-hydroxyquinoline-5-sulfonie acid TU—thiourea EDTA—ethylene-diamine tetraacetic acid zincon —2-carboxy-2 -hydroxy-5-sulformazylbenzene diamox — sodium 2 - acetylamino -1,3,4- thiodiazole - 5 - sulf onamide NaDDC — so -dium-diethyldithiocarbamate CGP—carbobenzoxyglycyl-L-phenylalanine. 

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