title: Kinetic, mutagenic, and structural homology analysis of L-serine dehydratase from Legionella pneumophila.
abstract: A structural database search has revealed that the same fold found in the allosteric substrate binding (ASB) domain of Mycobacterium tuberculosis D-3-phosphoglycerate dehydrogenase (PGDH) is found in l-serine dehydratase from Legionella pneumophila. The M. tuberculosis PGDH ASB domain functions in the control of catalytic activity. Bacterial l-serine dehydratases are 4Fe-4S proteins that convert l-serine to pyruvate and ammonia. Sequence homology reveals two types depending on whether their α and β domains are on the same (Type 2) or separate (Type 1) polypeptides. The α domains contain the catalytic iron-sulfur center while the β domains do not yet have a described function, but the structural homology with PGDH suggests a regulatory role. Type 1 β domains also contain additional sequence homologous to PGDH ACT domains. A continuous assay for l-serine dehydratase is used to demonstrate homotropic cooperativity, a broad pH range, and essential irreversibility. Product inhibition analysis reveals a Uni-Bi ordered mechanism with ammonia dissociating before pyruvate. l-Threonine is a poor substrate and l-cysteine and d-serine are competitive inhibitors with K(i) values that differ by almost 10-fold from those reported for Escherichia colil-serine dehydratase. Mutagenesis identifies the three cysteine residues at the active site that anchor the iron-sulfur complex.
authors: Department of Developmental Biology, Washington University School of Medicine, 660 S. Euclid Avenue, St. Louis, MO 63110, USA.
authors: Xiao Lan
authors: XL
authors: Xu
authors: Shawei
authors: S
authors: Chen
authors: Gregory A
authors: GA
authors: Grant
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D020134:Catalytic Domain; D017931:DNA Primers; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D012695:L-Serine Dehydratase / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000378:metabolism*; D016952:Legionella pneumophila / Q000201:enzymology*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009153:Mutagens; D011487:Protein Conformation; D017386:Sequence Homology, Amino Acid
chemical_list: D017931:DNA Primers; D009153:Mutagens; D012695:L-Serine Dehydratase