The Proposed Total Carbon Flow in CAM

Based on the arguments and evidence outlined above, the following general scheme of carbon flow for CAM is proposed. 

As outlined earlier in this chapter, the initial carboxylation product of CAM is oxalacetate. The oxalacetate is immediately reduced to malate or aminated to aspartate. It is malate or, more properly in CAM, malic acid which tends to accumulate. More than likely, through decarboxylation of malate, pyruvate is formed, some of which is aminated to alanine. Hence, the initial stable products of CAM are firstly malic acid, and then aspartate and alanine (Fig. 3.12). 

Other organic and amino acids such as citrate, isocitrate, a-ketoglutarate, succinate, glutamate, glycine, asparagine, and glutamine (see Table 3.1) are presumably synthesized through the usual intermediary metabolism reactions commonly known. 

By and large, no carbohydrates are produced in the dark, these are mostly produced in plants via photosynthetic dependent reactions. 

In the dark, it is assumed that stored starch or other glucan is hydrolyzed to sugar-phosphates which are metabolized to PEP via glycolysis and perhaps to some extent by pentose metabolism. Carboxylation of PEP results largely from atmospheric CO2 to give oxalacetate, which is immediately reduced to malate. Some oxalacetate will ultimately go into aspartate synthesis. Some of the malate will be decarboxylated to pyruvate (or perhaps PEP), where the 3-carbon frag- 

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