Glycine can be synthesized from all, EXCEPT:
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: Harper 28th edition, chapter 27.
Choline
Serine
Alanine
None of the above