glycine, the simplest amino acid, obtainable by hydrolysis of
proteins. Sweet-tasting, it was among the earliest amino acids
to be isolated from gelatin (1820). Especially rich sources
include gelatin and silk fibroin. Glycine is one of several so-
called nonessential amino acids for mammals; i.e., they can
synthesize it from the amino acids serine and threonine and from
other sources and do not require dietary sources. The chemical
structure of glycine is