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One of the amino acids, not essential for humans unless they have the hereditary disorder phenylketonuria. It is the biochemical precursor of many important catecholamines. It is found in small amounts in most proteins, especially insulin and papain (found in papaya). It is used in biochemical research and as a dietary supplement.
This entry comes from Encyclopædia Britannica Concise. For the full entry on tyrosine, visit Britannica.com.