title: Identification of nicotinamide mononucleotide deamidase of the bacterial pyridine nucleotide cycle reveals a novel broadly conserved amidohydrolase family.
abstract: The pyridine nucleotide cycle is a network of salvage and recycling routes maintaining homeostasis of NAD(P) cofactor pool in the cell. Nicotinamide mononucleotide (NMN) deamidase (EC 3.5.1.42), one of the key enzymes of the bacterial pyridine nucleotide cycle, was originally described in Enterobacteria, but the corresponding gene eluded identification for over 30 years. A genomics-based reconstruction of NAD metabolism across hundreds of bacterial species suggested that NMN deamidase reaction is the only possible way of nicotinamide salvage in the marine bacterium Shewanella oneidensis. This prediction was verified via purification of native NMN deamidase from S. oneidensis followed by the identification of the respective gene, termed pncC. Enzymatic characterization of the PncC protein, as well as phenotype analysis of deletion mutants, confirmed its proposed biochemical and physiological function in S. oneidensis. Of the three PncC homologs present in Escherichia coli, NMN deamidase activity was confirmed only for the recombinant purified product of the ygaD gene. A comparative analysis at the level of sequence and three-dimensional structure, which is available for one of the PncC family member, shows no homology with any previously described amidohydrolases. Multiple alignment analysis of functional and nonfunctional PncC homologs, together with NMN docking experiments, allowed us to tentatively identify the active site area and conserved residues therein. An observed broad phylogenomic distribution of predicted functional PncCs in the bacterial kingdom is consistent with a possible role in detoxification of NMN, resulting from NAD utilization by DNA ligase.
authors.affiliation: Department of Molecular Pathology and Innovative Therapies, Section of Biochemistry, Università Politecnica delle Marche, Ancona 60131, Italy.
authors.forename: Luca
authors.initials: L
authors.lastname: Galeazzi
authors.forename: Paola
authors.initials: P
authors.lastname: Bocci
authors.forename: Adolfo
authors.initials: A
authors.lastname: Amici
authors.forename: Lucia
authors.initials: L
authors.lastname: Brunetti
authors.forename: Silverio
authors.initials: S
authors.lastname: Ruggieri
authors.forename: Margaret
authors.initials: M
authors.lastname: Romine
authors.forename: Samantha
authors.initials: S
authors.lastname: Reed
authors.forename: Andrei L
authors.initials: AL
authors.lastname: Osterman
authors.forename: Dmitry A
authors.initials: DA
authors.lastname: Rodionov
authors.forename: Leonardo
authors.initials: L
authors.lastname: Sorci
authors.forename: Nadia
authors.initials: N
authors.lastname: Raffaelli
mesh_terms: D000581:Amidohydrolases / Q000235:genetics* / Q000378:metabolism; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics*; D029968:Escherichia coli Proteins / Q000235:genetics* / Q000378:metabolism; D016680:Genome, Bacterial / Q000502:physiology*; D009243:NAD / Q000235:genetics* / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D020592:Shewanella / Q000201:enzymology / Q000235:genetics
chemical_list: D029968:Escherichia coli Proteins; D009243:NAD; D000581:Amidohydrolases