Kinetic, mutagenic, and structural homology analysis of L-serine dehydratase from Legionella pneumophila

作者：Xu Xiao Lan; Chen Shawei; Grant Gregory A^*

来源：Archives of Biochemistry and Biophysics, 2011, 515(1-2): 28-36.

DOI：10.1016/j.abb.2011.08.005

• L-Serine
• Dehydratase
• Deaminase
• Iron-sulfur

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 a and 13 domains are on the same (Type 2) or separate (Type 1) polypeptides. The a domains contain the catalytic iron-sulfur center while the p domains do not yet have a described function, but the structural homology with PGDH suggests a regulatory role. Type 1 beta 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 coli L-serine dehydratase. Mutagenesis identifies the three cysteine residues at the active site that anchor the iron-sulfur complex.

• 出版日期2011-11