The Compartmentation of CAM Enzymes and Metabolites

P-enolpyruvate Carboxylase. P-enolpyruvate carboxylase activity was first reported by Bandurski and Greiner (1953) to be in extracts of spinach leaves. Later investigators, e.g., Mazelis and Vennesland (1957), Rosenberg et al. (1958), and 

In nonaqueously prepared chloroplasts from the succulent, Opuntia ficus-indica, NADP triose phosphate dehydrogenase maintained almost a constant ratio of activity to chlorophyll (Table 4.6), yet P-enolpyruvate carboxylase was not associated with chlorophyll on a constant basis. 

These data suggest that P-enolpyruvate carboxylase may not be associated with chloroplasts, and that it is not localized in the same subcellular compartment with NADP-triose phosphate dehydrogenase. Linear, nonaqueous gradient (CCl4-hexane) purification of chloroplasts indicate a particulate, but not a chloroplast localization of PEP carboxylase (Fig. 4.4). We conclude from these data that P-enolpyruvate carboxylase may be membrane-associated in situ, but the majority of the activity is not associated with chloroplasts, mitochondria, or microbodies. This conclusion is completely consistent with the metabolic compartmentation data. 

Malate Dehydrogenase. Most green plant tissues investigated appear to have three malate dehydrogenase loci two particulate loci, mitochondrial and microbody and a soluble or nonparticulate locus. Multiple forms can and do exist within a locus group (Mukerji and Ting, 1968). 

In addition, succulent plants have a chloroplast-specific NADP malate dehydrogenase analogous to the NADP form reported in C3 and C4 plants (Hatch and 

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