Three phases of research on beta-N-methylamino-L-alanine (BMAA)--a neurotoxic amino acid.

This paper discusses various aspects of the research that lead from the discovery of beta-N-methylamino-L-alanine (BMAA) to consider a variety of mechanisms that might explain the acute and chronic toxicities of this non-protein amino acid. Such is the fashion of science that current work represents the third phase of research on this compound over a period of more than 40 years. BMAA is now known to exist not only in the plant genus Cycas, where it is synthesized by symbiotic cyanobacteria in the coralloid roots of the plants, but to be widely distributed in the many sites at which free living cyanobacteria abound.