Characterization of NADP-malic enzyme from two species of Chenopodiaceae:: Haloxylon persicum (C4) and Chenopodium album (C3)

Kinetic and structural properties of NADP-malic enzyme (NADP-ME, E.C. 1.1.1.40) were analyzed from two members of the Chenopodiaceae family, Haloxylon persicum, an unusual C-4 NADP-ME type tree species native to Central Asia Deserts, and Chenopodium album, a C-3 weedy species. Two isoforms of the enzyme, with molecular masses of 67 and 72 kDa and pls (isoelectric points) of 6.75 and 5.85, respectively, were found in crude extracts of H. persicum by western blots using an antibody against the 62 kDa isoform from maize leaves. In C. album, a C3 plant, only one immunoreactive isoform, of 72 kDa was found, with an isoelectric point of 5.85. The 67 kDa isoform was purified from H. persicum shoots by precipitation with crystalline ammonium sulfate, anion-exchange, adsorption and affinity chromatographies. The 72 kDa isoform was purified from C. album in the same way, except that the adsorption chromatography step was omitted. The 67 kDa polypeptide of H. persicum was identified as a C-4 isoform based on its high specific activity, low K-m values for malate and NADP, and characteristics of its pH optima. However, this isoform is very different in molecular mass and isoelectric point from the previously characterized C-4 isoform found in C-4 monocots and C-4 Flaveria species. The 72 kDa isoform from C. album has kinetic properties which are distinct from the C-4 isoform of H. persicum, and characteristic of the low activity constitutive form found in various plants. (C) 1999 Elsevier Science Ltd. All rights reserved.