Dependence of Substrate Irradiation Reaction Rate Stimulation on Lactic Dehydrogenase Source

TL;DR

This study investigates how substrate irradiation affects enzyme reaction rates across different species, revealing species-specific stimulation times and a novel difference in separation times for chicken LDH.

Contribution

It demonstrates species-dependent variations in irradiation stimulation times and reports the first case of differing separation times for forward and reverse reactions in chicken LDH.

Findings

Mammalian enzymes stimulated at 5, 35 sec. for pyruvate and 15, 45 sec. for lactate.

Chicken enzyme shows shifted stimulation times: 15, 35 sec. for pyruvate and 5, 20 sec. for lactate.

First report of different separation times between forward and reverse reactions in LDH.

Abstract

Stimulation of LDH initial reaction rates by timed pre-irradiation of crystalline sodium pyruvate and lithium lactate is reported for enzymes isolated from rabbit muscle, pig heart, human erythrocytes and chicken heart. The phenomenon investigated is referred to as the Comorosan effect. For the mammalian source enzymes, the pyruvate irradiation stimulations occurred at irradiation times of 5 and 35 sec. and the lactate irradiation times at 15 and 45 seconds. In contrast, for the chicken heart enzyme, the pyruvate irradiation stimulations occurred at 15 and 35 sec., while those for lactate occurred at 5 and 20 sec. Thus, a shift in stimulatory irradiation times is found on going from the mammalian enzymes to the avian enzyme. A similar shift between mammalian and yeast enzymes has been established by Comorosan and co-workers. For the chicken heart LDH, the separation between successive irradiation times is different for the forward and reverse reactions. This is the first reported incidence of the separation not being the same.