A newly designed optical cell allows an enzyme reaction to be started under high pressure and makes it possible to begin measurement of the reaction rate after a ‘dead time’ no longer than 1–2 s. This device was used to study the kinetics of lactate dehydrogenase reaction at 1 kbar. At this pressure lactate dehydrogenase from rabbit muscle exhibited a rapid deactivation in the presence of NADH if pyruvate was absent. After addition of pyruvate the reaction was initiated and proceeded at a constant rate, i.e., without loss of enzyme activity. It is suggested that pyruvate markedly increases the association constant of this tetrameric enzyme.
