Characterization of a recombinant PEPC involved in C₄-photosynthesis in Eleocharis vivipara, a sedge interconvertible between C₃-and C₄- photosynthesis: Discovery of an C₄-form enzyme with unusually low K_m for PEP

Abstract

Eleocharis vivipara is an amphibious sedge which develops C₄ traits under terrestrial conditions and C₃ traits with non-Kranz anatomy under submerged conditions. The plant seems quite useful for the screening of genes and proteins which are indispensable for C₄ photosynthesis and for the elucidation of molecular mechanism for the integrated expression of C₄ genes. Since enzymatic properties of the C₄-form PEPC from this plant has not yet been studied, here we cloned a cDNA according to Agarie et al.(2002) and expressed in E. coli to prepare the recombinant PEPC (EvPEPC). A unique property of EvPEPC was that K_m for PEP was about 10-fold smaller than those for the C₄-form PEPCs from various C₄ species reported so far.
Several attempts were made to identify residues responsible for this unusual property by site-directed mutagenesis.