STEADY-STATE ENZYME VELOCITIES THAT ARE INDEPENDENT OF [ENZYME] - AN IMPORTANT BEHAVIOR IN MANY MEMBRANE AND PARTICLE-BOUND STATES

The popular paradigm for biological education in kinetics involves des criptions that are appropriate for soluble enzymes. Derivations seldom present the assumptions on which the fundamental parameter of these k inetics, the site rate constant, is based. This omission can create di fficulty for understanding situations where the assumptions are invali d. Membrane- and particle-bound enzyme systems provide several example s. In fact, biological organisms show macroscopic design and enzyme ex pression levels which suggest utilization of alternative kinetic mecha nisms. The role of substrate affinity and enzyme inhibitors is greatly altered, with correlated impact on biomedical and biotechnological de signs. Enzymes may perform functions such as isolation of cell content s from the environment, an action that is usually reserved for membran es. These properties can be mimicked but never perfectly replicated in purified systems. This presentation provides a description of some of these behaviors for membrane- or particle-bound enzymes, using an app roach that is closely correlated with the manner in which steady state enzyme kinetics are typically presented.