Proline, biosynthesis catabolism

Figure 28-8. Biosynthesis of proline from glutamate by reversal of reactions of proline catabolism.

Biochemical Functions. Ascorbic acid has various biochemical fimctions, involving, for example, coUagen synthesis, immune fimction, drug metabohsm, folate metabolism, cholesterol catabolism, iron metabolism, and carnitine biosynthesis. Clear-cut evidence for its biochemical role is available only with respect to coUagen biosynthesis (hydroxylation of prolin and lysine). In addition, ascorbic acid can act as a reducing agent and as an effective antioxidant. Ascorbic acid also interferes with nitrosamine formation by reacting directly with nitrites, and consequently may potentially reduce cancer risk. 

Polysaccharides, 44, 58 Prokaryote Cell, 7 Proline, 439 Promoters, 391 Protamines, 149 Proteans, 151 Protein Biosynthesis, 448 Protein Catabolism, 428 Protein Maturation, 449 Proteins, 262 Purine Metabolism, 379 Purines, 113 Pyridoxine, 229 Pyrimidines, 113 Pyruvate Kinase, 288... 

A variety of other enzymes involved in amino acid catabolism have been detected in both protozoa and helminths. These include deaminases such as histidase, decarboxylases, some of which are involved in biosynthesis of amines and related compounds, and hydroxylases of proline, tryptophan and tyrosine. These additional enzymes have mostly been reported in helminths (1). L-Amino acid oxidases and D-amino acid oxidases are also present and the availability of the latter would allow D-amino acids to be metabolized in the absence of amino acid racemases. 

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