Effect of Deuterium Oxide on Action of Some Enzymes

Abstract

Since the discovery of heavy water much speculation of very diverse character has been advanced in regard to its possible effects on life. The most extreme views are presented by those who claim, without adequate experimental proof, that deuterium oxide is a most powerful destructive physiological agent and those who, basing their conclusions on experiments made with deuterium oxide in dilute concentrations, state that its pharmacological effects are of negligible character. 1 , 2 , 3 The authors have recently discovered an interesting and striking contrast in the biophysical and biochemical behavior of H₂O and D₂O, which consists of a difference in velocity of reaction shown by certain animal and vegetable enzymes suspended therein. Studies were made on the behavior of muscle oxydase from the rat, of oxidative enzymes of fresh, blood-free brain tissue from the cat, and of reductase of finely ground seeds of Lupinus albus by the Thunberg method of determining the rapidity with which a standard buffered solution of methylene blue is decolorized in special vacuum tubes. Over 50 experiments were performed. The method employed is described in full elsewhere. 4 , 5 A marked difference was found to exist between identical enzymes suspended in H₂O and in the same kind of water to which small quantities of deuterium oxide had been added. This difference was demonstrated not only with concentrations of D₂O, 1:100, but also with concentrations of 1:2000 and less.

Further studies were made in connection with the influence of deuterium oxide on the activity of another enzyme, catalase. Catalase from fresh rat muscle and from Lupinus albus seeds in distilled water and in water to which small quantities of deuterium oxide were added also revealed a difference in the speed of evolution of oxygen gas from hydrogen peroxide in the presence of these enzymes.