Aspartate catabolism

Alanine. Transamination of alanine forms pyruvate. Perhaps for the reason advanced under glutamate and aspartate catabolism, there is no known metabolic defect of alanine catabolism. Cysteine. Cystine is first reduced to cysteine by cystine reductase (Figure 30-7). Two different pathways then convert cysteine to pyruvate (Figure 30-8). 

This pathway is the hub of intermediary metabolism. Four- and five-carbon end products of many catabolic processes feed into the cycle to serve as fuels. Oxaloac-etate and a-ketoglutarate, for example, are produced from aspartate and glutamate, respectively, when proteins are degraded. Under some metabolic circumstances, intermediates are drawn out of the cycle to be used as precursors in a variety of biosynthetic pathways. 

FIGURE 18-29 Catabolic pathway for asparagine and aspartate. Both amino acids are converted to oxaloacetate. 

Figure 2 Summary of the major oxidative routes for IAA catabolism. These include oxidation at the 2-position to form oxIAA and its metabolites (A and D), the recently described oxidations at indole-6 (B) and the formation of N-glucosides (C), and, finally, the conjugation to lAA-aspartate and its subsequent oxidation (E).

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