The glycine decarboxylase (GDC) or glycine cleavage system catalyzes the degradation of glycine. The P protein binds the alpha-amino group of glycine through its pyridoxal phosphate cofactor; CO(2) is released and the remaining methylamine moiety is then transferred to the lipoamide cofactor of the H protein (By similarity). (R)-N(6)-lipoyl-L-lysyl-[glycine-cleavage complex H protein] + glycine + H(+) = (R)-N(6)-(S(8)-aminomethyldihydrolipoyl)-L-lysyl-[glycine-cleavage complex H protein] + CO2 Inhibited by harpin, S-nitrosoglutathione (GSNO), nitric oxide, N-ethylmaleimide and 5,5'-dithiobis-(2-nitrobenzoic acid). Homodimer (By similarity). The glycine cleavage system is composed of four proteins: P, T, L and H. A number of isoforms are produced. According to EST sequences. Expressed in leaves. Detected in roots, stems, flowers and siliques. Glutathionylated at Cys-98, Cys-777, Cys-943 and Cys-1022 after S-nitrosoglutathione treatment. S-nitrosylated at unknown positions by nitric oxide. No visible phenotype; due to the redundancy with GLDP2. Gldp1 and gldp2 double mutants have a seedling development arrested at the cotyledon stage even under nonphotorespiratory conditions. Belongs to the GcvP family. This protein has also been shown to act as an inducible nitric oxide synthase (iNOS) (PubMed:12757708), but the paper has been retracted (PubMed:15599984).