C₄ plants possess two photosynthetic cells, mesophyll and bundle-sheath. In NAD-ME-(malic enzyme)-type C₄ plants, aspartate is transported from mesophyll to bundle-sheath mitochondria where it is transaminated to oxaloacetate by mitochondrial aspartate aminotransferase.

Oxaloacetate is further reduced to malate which is then decarboxylated to pyruvate by NAD-ME in the bundle-sheath mitochondria. The CO₂ released is refixed by RuBPCase localized in the bundle-sheath chloroplasts.

The decarboxylation product, pyruvate, is transported to the cytosol, transaminated to alanine via the action of alanine aminotransferase, and transported back to the mesophyll cells where it is transaminated to yield pyruvate in the cytosol.

Pyruvate is then converted to PEP by the chloroplast-localized pyruvate, orthophosphate dikinase (PPDK). PEP is then exported to the cytosol of the mesophyll cells and used for oxaloacetate synthesis in the reaction catalyzed by phosphoenolpyruvate carboxylase (PEPCase) (Taniguchi and Sugiyama, 1997).

Asp and Ala amintransferases are rapidly induced along with a suite of other C₄ pathway enzymes during induction of C₄-type photosynthesis in the submersed monocot Hydrilla verticillata (Magnin et al, 1997).

Kelly GL, Latzko E, Gibbs M 1976 Regulatory aspects of photosynthetic carbon metabolism. Annu. Rev. Plant Physiol. 27: 181-205.

Magnin NC, Cooley BA, Reiskind JB, Bowes G 1997 Regulation and localization of key enzymes during the induction of Kranz-less C₄-type photosynthesis in Hydrilla verticillata. Plant Physiol. 115: 1681-1689.

Taniguchi M, Sugiyama T 1997 The expression of 2-oxoglutarate/malate translocator of Panicum miliaceum, a NAD-malic enzyme-type C₄ plant, is regulated by light and development. Plant Physiol. 114: 285-293.