Type III Pyridoxal 5-phosphate (PLP)-Dependent Enzyme Eukaryotic D-Serine Dehydratase
This subfamily is composed of chicken D-serine dehydratase (DSD, EC 184.108.40.206) and similar eukaryotic proteins. Chicken DSD catalyzes the dehydration of D-serine to aminoacrylate, which is rapidly hydrolyzed to pyruvate and ammonia. It is a fold type III PLP-dependent enzyme with similarity to bacterial alanine racemase (AR), which contains an N-terminal PLP-binding TIM-barrel domain and a C-terminal beta-sandwich domain. AR exists as dimers with active sites that lie at the interface between the TIM barrel domain of one subunit and the beta-sandwich domain of the other subunit. Experimental data suggest that chicken DSD also exists as dimers. Sequence comparison and biochemical experiments show that chicken DSD is distinct from the ubiquitous bacterial DSDs coded by dsdA gene, mammalian L-serine dehydratases (LSD) and mammalian serine racemase (SerRac), which are fold type II PLP-dependent enzymes.