Pressure-adaptive differences in lactate dehydrogenases of congeneric fishes living at different depths.

The muscle-type (M4) lactate dehydrogenases of Sebastolobus altivelis, a deep-water scorpaenid, and S. alascanus, a shallower species, are electrophoretically indistinguishable, yet differ in pressure sensitivities. The lactate dehydrogenase of S. altivelis exhibits lower pressure sensitivities of substrate and coenzyme binding and catalytic rate. Such apparently pressure-adaptive kinetic properties may be important for establishing species depth zonation patterns in the ocean.