Conformation change alcohol dehydrogenase

W. R. Laws and J. D. Shore, Spectral evidence for tyrosine ionization linked to a conformational change in liver alcohol dehydrogenase ternary complexes, J. Biol. Chem. 254, 2582-2584 (1979). 

The specificities of the enzymes are also nicely explained The enantiomers of the substrates of L-lactate and D-glyceraldehyde 3-phosphate dehydrogenases cannot be productively bound the hydrophobic pocket of alcohol dehydrogenase will not bind the charged side chains of lactate etc. However, we do not know if conformational changes occur during catalysis or if there is strain. 

Alcohol oxidation requires release of a proton, which formally comes from the alcohol. In other dehydrogenases such as lactate dehydrogenase, proton release occurs simultaneously with hydride transfer. In liver ADH proton release can be demonstrated, by reaction of the proton with an indicator such as thymol blue or phenol red in stopped-flow spectrophotometry, to be faster than hydride transfer, 270 vs. 150 s and unaffected by use of deuterated substrate, so it occurs before hydride transfer. Binding of the NAD+ nicotinamide ring is accompanied by a conformational change of ADH bringing the catalytic zinc about 0.1 nm closer to the... 

When trying to determine the 3D structure of binary and ternary complexes of Drosophila alcohol dehydrogenase (DADH), researchers initial attempts to soak apo-form crystals with the oxidized coenzyme (NAD+) failed. The crystals cracked after several hours and became unusable. This suggested that the coenzyme, upon binding to the enzyme, induced a conformational change that seriously affected the crystal packing. The same phenomenon prevented solution of the HL-ADH 3D structure for many years. 

Branden, C.-l., Ekiund, H. Coenzyme-induc conformational changes and substrate binding in liver alcohol dehydrogenase in Molecular Interactions and Activity in Proteins, Ciba Foundation Symp. 60 (New Kries), pp. 63-80, Ezceipta M Uca, Amsterdam, 1978... 

Tapia and Eklund (1986) carried out a Monte Carlo simulation of the substrate channel of liver alcohol dehydrogenase, based on the X-ray diffraction structure for this enzyme. The addition of substrate and the associated conformation change induce an order—disorder transition for the solvent in the channel. A solvent network, connecting the active-site zinc ion and the protein surface, may provide the basis for a proton relay system. A molecular dynamics simulation of carbonic anhydrase showed two proton relay networks connecting the active-site zinc atom to the surrounding solvent (Vedani et ai, 1989). They remain intact when the substrate, HCOf, is bound. 

Yeast Alcohol Dehydrogenase. Conformational changes are known to play an important role in the mechanism of enzyme action. The existence of conformational changes in enzymes bound to coenzymes or substrates has been postulated by several investigators (Nozaki et al., 1957 Sekuzu et al., 1957 Yonetani and Theorell, 1962 DiSabato and Kaplan, 1964 DiSabato and Kaplan, 1965). Hvidt and her... 

The mechanism of this oxidation for the enzyme liver alcohol dehydrogenase is shown for the reaction of 83, where ethanol is bound to the active site of the enzyme to give 84 via proton abstraction and then hydride transfer to generate acetaldehyde (see 85). NAD+ binds to the active site of the enzyme to induce a conformational change (see Chapter 8 for conformation) to close the active site. The oxidation of ethanol to acetaldehyde (ethanal) is accompanied by reduction of NAD+ to NADH, as shown in the illustration. 

Sachsenheimer and Schulz report the structure of another crystalline form of adenylate kinase which appears to be related to the previously known form by a conformation change in a segment. The binding sites of ATP and AMP to this enzyme were also located. Similar work on the identification of binding sites and the assessment of conformational changes has been continued with ribo-nuclease, alcohol dehydrogenase, concanavalin A, " hexokinase, lysozyme," flavodoxin, and oxy-erythrocrurin." ... 

Alcohol dehydrogenase serves as an example of an enzyme reaction which involves proton uptake and release during a substrate induced conformation change, and also as part of the stoichiometry of the reaction catalysed. The present discussion is only intended to deal with certain elementary steps without going into the detail of the whole reaction mechanism (see section 5.1). The reaction catalysed by this enzyme... 

Dallet, S. and Legoy, M.-D. (1996) Hydrostatic pressure induces conformational and catalytic changes on two alcohol dehydrogenases but no oligomeric dissociation. Biochimica et Biophysica Acta, 1294, 15-24. 

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