Threonine dehydratase: The first step in amino acid degradation is the removal of nitrogen. Although the nitrogen atoms of most amino acids are transferred to alpha-ketoglutarate before removal, the alpha-amino group of threonine can be directly converted into NH4+. The direct deamination is catalyzed by threonine dehydratase, in which pyridoxal phosphate (PLP) is the prosthetic group. Threonine dehydratase is widely distributed in all three major phylogenetic divisions.
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