Hydrostatic pressure induces conformational and catalytic changes on two alcohol dehydrogenases but no oligomeric dissociation.

A comparison between the pressure effects on the catalysis of Thermoanaerobium brockii alcohol dehydrogenase (TBADH: a thermostable tetrameric enzyme) and yeast alcohol dehydrogenase (YADH: a mesostable tetrameric enzyme) revealed a different behaviour. YADH activity is continuously inhibited by an increase of pressure, whereas YADH affinity seems less sensitive to pressure. TBADH activity is enhanced by pressure up to 100 MPa. TBADH affinity for alcoholic substrates increases if pressure increases, was TBADH affinity for NADP decreases when pressure increases. Hypothesis has been raised concerning the dissociation of oligomeric enzymes under high hydrostatic pressure ( < 200 MPa) [1]. But in the case of these two enzymes, unless the oligomers reassociate very quickly (< 1 min), the activity inhibition of YADH at all pressures and TBADH for pressures above 100 MPa is not correlated to subunit dissociation. Hence we suggest that enzymes under pressure encounter a molecular rearrangement which can either have a positive or a negative effect on activity. Finally, we have observed that the catalytic behaviour of alcohol dehydrogenases under pressure is connected to their thermostability.