Ribozymes: analytical solution of the one-substrate, two-intermediate reversible scheme for enzyme reactions.

The paper presents a kinetic analysis of a reversible enzymatic reaction Sright arrow over left arrowP involving two intermediate compounds under the condition [E](0) >> [S](0) + [P](0). For the case of mono-exponential behavior, we derive an equation for k (obs) as a function of [E](0), which emphasizes the pitfalls of oversimplifying kinetic schemes (such as the Michaelis-Menten model) for ribozyme studies. This novel apparent rate constant, which has been arrived at through mechanistic considerations, is analyzed, and the characteristic parameters obtained. The equation, which seems to fit experimental data better than conventional approximations, is used to analyze a single turnover study on an ADC1 ribozyme drawn from hepatitis delta virus RNA. The microscopic kinetic constants for such enzyme are evaluated and its mono-exponential behavior verified.