The pressure-induced inactivation of mammalian enolases is accompanied by dissociation of the dimeric enzyme.
The effects of exposure to pressure on both the activity and the quaternary structure of rabbit brain enolases, forms alpha alpha, alpha gamma, and gamma gamma were studied in the pressure range of 1 to 3400 bar. Effects on quaternary structure were determined by subunit scrambling (the formation of alpha alpha and gamma gamma from alpha gamma or vice versa). All three dimers are stable up to pressures of 1200 bar. The dissociation of gamma gamma begins at 1200 bar, yielding a stable monomer; inactivation of gamma gamma does not begin until the pressure is greater than 2000 bar. Dissociation of gamma gamma is not accompanied by changes in the tryptophan fluorescence of the protein. However, the fluorescence does decrease when the pressure is greater than 2000 bar, the point at which inactivation of gamma gamma starts. The alpha monomer, on the other hand, is unstable in the pressure range that produces dissociation of alpha alpha. This process, which also begins at 1200 bar, is paralleled by inactivation. Crosslinking the enzyme with glutaraldehyde demonstrated that the inactive form of the enzyme is monomeric. The pressure-induced inactivation of these forms of enolase is thus clearly a two-step process, with both dissociation and inactivation occurring. The difference in pressure sensitivity of rabbit brain alpha alpha and gamma gamma is due to a difference in stability of the alpha and gamma monomers and not due to a difference in the pressures required for dissociation.
D000818:Animals; D001921:Brain / Q000201:enzymology*; D003432:Cross-Linking Reagents; D004591:Electrophoresis, Polyacrylamide Gel; D005470:Fluorometry; D005976:Glutaral; D007527:Isoenzymes / Q000378:metabolism*; D046911:Macromolecular Substances; D008970:Molecular Weight; D010751:Phosphopyruvate Hydratase / Q000378:metabolism*; D011312:Pressure; D011817:Rabbits
D003432:Cross-Linking Reagents; D007527:Isoenzymes; D046911:Macromolecular Substances; D010751:Phosphopyruvate Hydratase; D005976:Glutaral