Kinetics of the Inhibition of Cypridina Luciferase by Specific Antibody

Abstract

A kinetic study of the antigen-antibody reaction involving specific rabbit antibody to luciferase, the enzyme responsible for the blue luminescence of the marine crustacean, Cypridina hilgendorfii, was carried out by a quantitative photometric method. Interaction of antibody and luciferase resulted in inactivation of the enzyme. Investigation of the rate of inactivation over a 100,000-fold range in antibody concentration showed the rate to be concentration dependent. The reaction equilibrium was represented by a sigmoid curve. At antibody excess, the inactivation obeyed pseudounimolecular kinetics during the initial 14 min, after which the rate decreased. Luciferase activity was inhibited by one molecule of antibody acting noncompetitively. The inhibition was partially reversible by simple dilution. The rate of inactivation was pH dependent, with an optimum of around 5.4. The data suggest that ionic attraction plays a significant role in the inactivation process.