gamma-Glutamylmethionine is a dipeptide composed of gamma-glutamate and methionine, and is a proteolytic breakdown product of larger proteins. It belongs to the family of N-acyl-alpha amino acids and derivatives. These are compounds containing an alpha amino acid which bears an acyl group at its terminal nitrogen atom. gamma-Glutamylmethionine is an incomplete breakdown product of protein digestion or protein catabolism. Some dipeptides are known to have physiological or cell-signaling effects although most are simply short-lived intermediates on their way to specific amino acid degradation pathways following further proteolysis. gamma-Glutamylmethionine is found in onion-family vegetables. It is isolated from the seeds of onion (Allium cepa), kidney bean (Phaseolus vulgaris), mung bean (Vigna radiata), garlic (Allium sativum), and black gram (Vigna mungo).