Phosphoenolpyruvic carboxylases photosynthesis

C4 plants concentrate their Calvin cycle photosynthesis in specialized bundle sheath cells, which lie below a layer of mesophyll cells (Figure 17.25). The mesophyll cells, which are most directly exposed to external C02, contain the enzymes of the C4 cycle. See Figure 17.26 for the reactions of the C4 cycle. The key reaction, which is the capture of C02 into oxaloacetate, is catalyzed by the enzyme phosphoenolpyruvate carboxylase and occurs in the mesophyll cells. 

Downton,W.J.S. Adaptive and evolutionary aspects of C4 photosynthesis. In Photosynthesis and photorespiration. Hatch,M.D., Osmond,C.B., Slatyer,R.O. (eds.), pp. 3-17. New York, London, Sydney, Toronto Wiley-Interscience 1971 Eickmeier,W.G., Bender, M.M. Carbon isotope ratios of Crassulacean Acid Metabolism species in relation to climate and phytosociology. Oecologia 25,341-347 (1976) Enama,M. Molecular weight variations of phosphoenolpyruvate carboxylase from C4 plants. Carnegie Inst. Yearb. 75,409-413 (1976)... 

In plants and bacteria, an enzyme not found in animal tissues, phosphoenolpyruvate carboxylase, may convert phosphoenolpyruvate into oxaloacetate without the requirement of a nucleoside triphosphate or biotin. The enzyme also has an important role in photosynthesis (Section 14.5). 

Hudspeth, R.L. and J.W. Grula. 1989. Structure and expression of the maize gene encoding the phosphoenolpyruvate carboxylase isozyme involved in C4 photosynthesis. Plant Mol. Biol. 12 579-589. 

---