STUDIES ON CELL ENZYME SYSTEMS. VII. LUCIFERASE INACTIVATION BY ALCOHOLS

¹ Physiological Laboratories, Princeton University, New Jersey, and the Marine Biological Laboratory, Woods Hole, Massachusetts

The luminescent reaction of partially purified Cypridina luciferase and luciferin was measured in the presence of various concentrations of methanol, ethanol, 1-propanol, 1-butanol, 1-pentanol, and 1-hexanol.

The relative first order velocity constant of the reaction, representing luciferase activity, decreased reversibly with increasing alcohol concentration. Also, each additional methylene group in the alcohol increased its effectiveness about two and a half times. Analysis of the data in terms of a mass law equation indicated that, if certain apparently non-random variations were attributed to experimental error, about one and a half alcohol molecules combined with one enzyme molecule (or active catalytic site) in producing inactivation.

For 50 per cent inactivation of the enzyme the thermodynamic activity (mol fraction of alcohol times its activity coefficient) of the six alcohols increased in a regular way with increase in their chain length.

The total light emitted in the luminescent reaction, probably representing the substrate, luciferin, was also affected by the three lower alcohols in the series, although the three higher ones could not be studied in this respect because relatively low concentrations completely inactivated the enzyme. The effect on the total light, in contrast with that on the enzyme, appeared to be relatively nonspecific, since approximately equal effects were produced by equal concentrations of the three alcohols which were studied.