The glycine decarboxylase (GDC) or glycine cleavage system catalyzes the degradation of glycine. The H protein shuttles the methylamine group of glycine from the P protein to the T protein. Binds 1 lipoyl cofactor covalently. Inhibited by harpin, S-nitrosoglutathione (GSNO), nitric oxide, N-ethylmaleimide and 5,5'-dithiobis-(2-nitrobenzoic acid). The glycine cleavage system is composed of four proteins: P, T, L and H. Highly expressed in leaves, lower expression in green veins, petioles, and stems, and detected in roots. Up-regulated by light. S-nitrosylated and/or glutathionylated at unknown positions in response to nitric oxide. Belongs to the GcvH family.