Glycine dehydrogenase (cytochrome)

Glycine dehydrogenase (cytochrome), often abbreviated as GDH(cytochrome) or GcvH (Glycine cleavage system H protein), is an enzyme involved in the glycine cleavage system, a crucial metabolic pathway found in bacteria, plants, and animals. Specifically, it participates in the oxidative decarboxylation of glycine.

In the glycine cleavage system, GDH(cytochrome) catalyzes the transfer of a methylamine group from tetrahydrofolate (THF) to the aminomethyl carrier protein, H-protein. This reaction is a key step in the degradation of glycine and the subsequent formation of carbon dioxide, ammonia, and NADH. The H-protein, with its lipoyl moiety, is essential for accepting the aminomethyl group.

The systematic name for this enzyme is glycine:cytochrome oxidoreductase (decarboxylating, aminomethyl-transferring). The enzyme belongs to the oxidoreductase class, acting on CH-NH2 group of donors with a cytochrome as an acceptor.

The glycine cleavage system plays a vital role in photorespiration in plants, where it recycles phosphoglycolate generated during photosynthesis. In animals and bacteria, it contributes to the regulation of glycine levels and provides one-carbon units for various biosynthetic pathways. Deficiencies in components of the glycine cleavage system, including GDH(cytochrome), can lead to nonketotic hyperglycinemia (NKH), a severe metabolic disorder characterized by elevated glycine levels in bodily fluids.