High pressure effects on the activity of glycolytic enzymes.

High hydrostatic pressure inhibits growth in most organisms; this may be explained by a deactivation of enzymes involved in essential metabolic pathways. In order to check this hypothesis the enzymic activity of rabbit muscle lactic dehydrogenase and yeast glyceraldehyde-3-phosphate dehydrogenase was investigated in the presence of the coenzyme and excess of substrate at pressures up to 2kbar. Kinetic analysis of an initial phase of pressure induced activation and of a second phase of reversible deactivation shows that the two enzymes respond to high pressures in different ways leading to a volume of activation of increment V is not equal to (LDH) equal 0 plus or minus 1 cm-3 mol-1 and increment V is not equal to (GAPDH) equals 60 plus or minus 4 cm-3 mol-1, respectively. Comparing the lower limits of pressure deactivation, LDH is found to be more stable towards pressure than GAPDH. At p is approximately equal to 2 kbar total deactivation of both enzymes is observed. A concentration dependent lag of GAPDH reactivation proves dissocation to participate in the process of deactivation, while the effects for LDH are explicable on the basis of reversible denaturation alone.