Abstract
During the last decade great progress has been made in the study of the intensity factor in oxidation-reduction equilibria. The investigations of Mansfield Clark and others have made possible the quantitative determination of this factor both in vitro and in vivo.
It has been known for a long time that the activity of the several enzymes essential in life processes is conditioned by a variety of factors, such as temperature, the nature and concentration of electrolytes (notably the hydrogen ion concentration), the dilution of enzyme and of substrate, irradiation. 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 It seems probable on a priori grounds that in the case of some enzymes, the oxidation-reduction potential of the system may be important. The experiments of Stephenson 10 which showed a relation between pH and rate of reduction of lactic acid by dehydrogenase, are interesting in this connection.
We have undertaken the study of enzyme action in buffered systems in which the oxidation-reduction potential is kept constant—precautions not hitherto observed as far as we know. The first case investigated was the hydrolysis of starch by takadiastase.
Known amounts of indicator and of starch were incubated at 37.5° in solutions buffered at pH 5.9 (optimal for takadiastase) and poised at various oxidation-reduction potentials, and the maltose formed in the experimental and control tubes was determined at the end of a 30-minute period. To prevent oxidation of the reduced dyes, the reactions were carried out in an atmosphere of oxygen-free nitrogen, which was first passed through a furnace of finely divided copper heated to 750°C. to remove traces of oxygen. The several gas outlet tubes led to one common tube, to insure equal pressure in all vessels, and the tip of this latter tube dipped in mercury to prevent back diffusion of oxygen.
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