Pyruvate,Pi Dikinase and NADP-Malate Dehydrogenase in C4 Photosynthesis: Properties and Mechanism of Light/Dark Regulation

[Extract] C4 Cycle and its Significance in Photosynthesis This review considers two key enzymes of the C4 pathway of photosynthesis, pyruvate,Pi dikinase (PPDK) and NADP-malate dehydrogenase (NADPMDH). I Besides their critical roles in C4 photosynthesis, these enzymes also share in common the fact that their activity is rapidly modulated by changes in light intensity. We will describe the radically different mechanisms by which this light-mediated modulation of activity is achieved . The kinetic and physical properties of these enzymes, and other mechanisms by which they are regulated, will also be reviewed. There have been recent reviews of the biochemistry of C4 photosynthesis (28, 31) and the light modulation of other photosynthetic enzymes, particularly in C3 plants (1-3, 16-18), so these areas will not be covered here.