HealthWise® L-Tyrosine is a 100% pure pharmaceutical grade amino acid. Tyrosine is found in many high protein foods and is synthesized in the body from the amino acid phenylalanine. L-Tyrosine plays a role as a precursor to various neurotransmitters and hormones found in the human brain. Did you know? The word 'tyrosine' is from the greek tyros, meaning cheese, as it was first discovered in 1846 by German chemist Justus von Liebig in the protein casein from cheese.