In mammalian tissue, glycine is synthesized from the following precursors:

Glycine aminotransferases can catalyze the synthesis of glycine from glyoxylate and glutamate or alanine. Unlike most aminotransferase reactions, these strongly or glycine synthesis. Additional impoant mammalian routes for glycine formation are from choline and from serine. Ref: Rodwell V.W. (2011). Chapter 27. Biosynthesis of the Nutritionally Nonessential Amino Acids. In D.A. Bender, K.M. Botham, P.A. Weil, P.J. Kennelly, R.K. Murray, V.W. Rodwell (Eds), Harper's Illustrated Biochemistry, 29e.