This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via CrossRef Citing Articles via Google Scholar Google Scholar Articles by Willeford, K. O. Articles by Wedding, R. T. Search for Related Content PubMed PubMed Citation Articles by Willeford, K. O. Articles by Wedding, R. T. Agricola Articles by Willeford, K. O. Articles by Wedding, R. T.

Articles

Regulation of the NAD Malic Enzyme from Crassula¹

Department of Biochemistry, University of California, Riverside, California 92521

Using size exclusion chromatography, the nicotinamide adenine dinucleotide malic enzyme purified to near homogeneity from leaves of Crassula argentea was found to exist in at least three aggregational states (dimer, tetramer, and octamer). These forms differ in their apparent kinetic characteristics in initial rate assays, but all display similar characteristics at the steady state. The presence of 50 millimolar malate during chromatography causes a shift in favor of the smaller forms with the tetramer predominating. The native enzyme, when diluted 1/1000 and incubated 18 hours in buffer of high ionic strength, changes its steady state kinetic parameters to ones which indicate a low activity and low affinity for malate. When 50 millimolar malate or 50 micromolar coenzyme A are present the loss of activity and increase in K_m is reduced. When both malate and coenzyme A are present the effects in minimizing the change in kinetic characteristics are additive.