Properties and mechanism of d-glucosaminate-6-phosphate ammonia-lyase: An aminotransferase family enzyme with d-amino acid specificity

Publication date: Available online 23 December 2017 Source:Biochimica et Biophysica Acta (BBA) - Proteins and Proteomics Author(s): Robert S. Phillips, Samuel C. Ting, Ange G. Tetsadjio, Kaitlin L. Anderson, Kyle M. Friez, Katherine A. Miller, Timothy R. Hoover Salmonella enterica serovar Typhimurium utilizes a wide range of growth substrates, some of which are relatively novel. One of these unusual substrates is d-glucosaminate, which is metabolized by the enzymes encoded in the dga operon. d-Glucosaminate is transported and converted to d-glucosaminate-6-phosphate (G6P) by a phosphotransferase system, composed of DgaABCD. The protein product of dgaE, d-glucosaminate-6-phosphate ammonia lyase (DGL), converts G6P to 2-keto-3-deoxygluconate-6-phosphate, which undergoes a retroaldol reaction catalyzed by the DgaF protein to give d-glyceraldehyde-3-phosphate and pyruvate. We have now developed an improved synthesis of G6P which gives a higher yield. The DGL reaction is of mechanistic interest because it is one of only a few enzymes in the pyridoxal-5′-phosphate (PLP) dependent aminotransferase superfamily known to catalyze reaction of a d-amino acid substrate. The pH dependence of DGL shows an optimum at 7.5–8.5, suggesting a requirement for a catalytic base. α-Glycerophosphate and inorganic phosphate are weak competitive inhibitors, with Ki values near 30mM, and d-serine is neither a substrate nor an inhibitor. We have found in rapid-scanning stopped-flow experime...
Source: Biochimica et Biophysica Acta (BBA) Proteins and Proteomics - Category: Biochemistry Source Type: research