Kinetic Analysis of Parallel Reactions, the Initial Reactant of which Presents with two Interconvertible Isomeric Forms (hydrolysis and hydroxylaminolysis of 6-phosphogluconolactone)

A mathematical treatment is presented of two parallel reactions each one of which can be described by the sum of two exponential functions of time. The two simplest reaction models consistent with this requirement are presented, and are shown to be described by a second-order non-homogeneous differential equation with constant coefficients. Solutions of this equation in closed form are given, and it is shown that, as is the case with pairs of parallel first-order reactions, description of the time course of one of the two reactions yields a complete description of the time course of the other reaction. Hypothetical cases, consistent with the reaction models presented, are given and are compared with experimental results, obtained on the parallel reactions of 6-phosphogluconolactone hydrolysis and hydroxylaminolysis. Results are compatible with the existence of enzymically generated 6-phosphogluconolactone in two interconvertible isomeric forms.