Isotope partitioning for NAD-malic enzyme from Ascaris suum confirms a steady-state random kinetic mechanism
- 1 January 1988
- journal article
- research article
- Published by American Chemical Society (ACS) in Biochemistry
- Vol. 27 (1) , 212-219
- https://doi.org/10.1021/bi00401a032
Abstract
Isotope partitioning studies beginning with E.cntdot.[14C]NAD, E.cntdot.[14C]malate, E.cntdot.[14C]NAD.cntdot.Mg2+, and E.cntdot.Mg.cntdot.[14C]malate suggest a steady-state random mechanism for the NAD-malic enzyme. Isotope trapping beginning with E.cntdot.[14C]NAD and with varying concentrations of Mg2+ and malate in the chase solution indicates that Mg2+ is added in rapid equilibrium and must be added prior to malate for productive ternary complex formation. Equal percentage trapping from E.cntdot.[14C]NAD.cntdot.Mg and E.cntdot.Mg.cntdot.[14C]malate indicates the mechanism is steady-state random with equal off-rates for NAD and malate from E.cntdot.NAD.cntdot.Mg.cntdot.malate. The off-rates for both do not change significantly in the ternary E.cntdot.Mg.cntdot.malate and E.cntdot.NAD.cntdot.Mg complexes, nor does the off-rate change for NAD from E.cntdot.NAD. No trapping of malate was obtained from E.cntdot.[14C]malate, suggesting that this complex is nonproductive. A quantitative analysis of data allows an estimation of values for a number of the rate constants along the reaction pathway.This publication has 1 reference indexed in Scilit:
- Purification of malic enzyme from Ascaris suum using NAD+-agaroseMolecular and Biochemical Parasitology, 1981