Glycine cleavage system P protein <p>The P protein is part of the glycine decarboxylase multienzyme complex (GDC), also annotated as glycine cleavage system or glycine synthase. GDC consists of four proteins P, H, L and T [<cite idref="PUB00009491"/>]. The P protein (<db_xref db="EC" dbkey="1.4.4.2"/>) binds the alpha-amino group of glycine through its pyridoxal phosphate cofactor, carbon dioxide is released and the remaining methylamin moiety is then transferred to the lipoamide cofactor of the H protein. The reaction catalysed by this protein is:</p><reaction> Glycine + lipoylprotein = S-aminomethyldihydrolipoylprotein + CO2 </reaction><p>The subunit composition of glycine cleavage system P proteins have been classified into two types. Those from eukaryotes and some of the P proteins from prokaryotes (e.g. <taxon tax_id="562">Escherichia coli</taxon>) are in the homodimeric form. The rest of those from prokaryotes are heterotetrameric, with two different subunits which, based on sequence similarities, correspond respectively to the N and C-terminal halves of the eukaryotic subunit [<cite idref="PUB00038183"/>].</p>