Influence of polyol additive on enzyme catalytic selectivity towards different substrates.
Sorbitol, added as a depressor of water activity in the reaction medium of yADH, can modify the kinetic behaviour of the enzyme towards the four substrates tested: ethanol, propanol, butanol and pentanol, as well as towards the coenzyme NAD. All apparent Km values of the alcohol substrates and NAD decreased as the additive concentration increased. However, the additive-caused modifications of the enzyme activity were found to depend on the carbon-chain length of the alcohol substrate, in other words, the catalytic selectivity of the enzyme towards different substrates was changed by the additive. These results and supplementary experiments suggested that sorbitol may have two opposing effects on the enzyme: the positive effect leads the enzyme to adopt a conformation which is more accessible to its substrates; while the negative effect results in a diffusional constraint for the enzyme reaction. Observed results were the combination of the two opposing effects.
Xu
Z F
ZF
Laboratoire de Technologie Enzymatique, Université de Technologie de Compiègne, France.
Larreta-Garde
V
V
Thomas
D
D
D000433:1-Propanol / Q000378:metabolism; D000426:Alcohol Dehydrogenase / Q000378:metabolism*; D001665:Binding Sites; D000440:Butanols / Q000378:metabolism; D000431:Ethanol / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D009243:NAD / Q000378:metabolism; D000439:Pentanols / Q000378:metabolism; D011487:Protein Conformation; D012967:Sodium Dodecyl Sulfate / Q000494:pharmacology; D013012:Sorbitol / Q000494:pharmacology*
D000440:Butanols; D000439:Pentanols; D009243:NAD; D012967:Sodium Dodecyl Sulfate; D000431:Ethanol; D013012:Sorbitol; D000433:1-Propanol; D000426:Alcohol Dehydrogenase