Toxic Nonprotein Amino Acids
- Publication Type:
- Plant Toxins, 2015, pp. 1 - 20
- Issue Date:
The 20 DNA-coded protein amino acids play central roles in the metabolism of most organisms. As well as being the building blocks for proteins, they play essential roles in a diverse range of metabolic pathways. They are estimated to be around 1000 molecules in nature, which share the same basic structure as these organic amino acids consisting of an α-carbon attached to a carboxyl group, an amino group, a hydrogen atom, and a unique side-chain group. Many “nonprotein” amino acids (NPAAs) are plant secondary metabolites. In this chapter, the authors discuss plant NPAAs that have a similar chemical structure, size, shape, and charge to protein amino acids and can be mistakenly used in protein synthesis, interfere in biochemical pathways, overstimulate receptors, or chelate metal ions. Most often this results in some level of toxicity to the target organism and can confer some advantage to the plant. Toxic NPAAs might have evolved as defense chemicals that can be released into the soil to inhibit the growth of other plants or agents that can limit insect herbivory. The effects of NPAAs on human health are not well understood. Consumption of a number of plants that contain NPAAs has been shown to have acutely toxic effects in humans. The key questions that remain unanswered are to what extent can NPAAs enter the food chain and what are the effects of a chronic low-level exposure to toxic plant NPAAs?
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