Type III Pyridoxal 5-phosphate (PLP)-Dependent Enzyme Bacterial Cryptic D-Serine Dehydratase
This subfamily is composed of Burkholderia cepacia cryptic D-serine dehydratase (cryptic DSD), which is also called D-serine deaminase, and similar bacterial proteins. Members of this subfamily are fold type III PLP-dependent enzymes 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. Based on similarity, it is possible cryptic DSDs may also form dimers. Cryptic DSDs are distinct from the ubiquitous bacterial DSDs coded by the dsdA gene, mammalian L-serine dehydratases (LSD) and mammalian serine racemase (SerRac), which are fold type II PLP-dependent enzymes. At present, the enzymatic and biochemical properties of cryptic DSDs are still poorly understood. Typically, DSDs catalyze the dehydration of D-serine to aminoacrylate, which is rapidly hydrolyzed to pyruvate and ammonia.