National Center for
5C3U: Crystal Structure Of A Fungal L-serine Ammonia-lyase From Rhizomucor Miehei
Biochem. Biophys. Res. Commun. (2015) 466 p.431-437
l-serine ammonia-lyase, as a member of the beta-family of pyridoxal-5'-phosphate (PLP) dependent enzymes, catalyzes the conversion of l-serine (l-threonine) to pyruvate (alpha-ketobutyrate) and ammonia. The crystal structure of l-serine ammonia-lyase from Rhizomucor miehei (RmSDH) was solved at 1.76 A resolution by X-ray diffraction method. The overall structure of RmSDH had the characteristic beta-family PLP dependent enzyme fold. It consisted of two distinct domains, both of which show the typical open twisted alpha/beta structure. A PLP cofactor was located in the crevice between the two domains, which was attached to Lys52 by a Schiff-base linkage. Unique residue substitutions (Gly78, Pro79, Ser146, Ser147 and Thr312) were discovered at the catalytic site of RmSDH by comparison of structures of RmSDH and other reported eukaryotic l-serine ammonia-lyases. Optimal pH and temperature of the purified RmSDH were 7.5 and 40 degrees C, respectively. It was stable in the pH range of 7.0-9.0 and at temperatures below 40 degrees C. This is the first crystal structure of a fungal l-serine ammonia-lyase. It will be useful to study the catalytic mechanism of beta-elimination enzymes and will provide a basis for further enzyme engineering.