title: Combined Whole-Cell High-Throughput Functional Screening for Identification of New Nicotinamidases/Pyrazinamidases in Metagenomic/Polygenomic Libraries.
abstract: Nicotinamidases catalyze the hydrolysis of the amide bond in nicotinamide (NAM) to produce ammonia and nicotinic acid (NA). These enzymes are an essential component of the NAD+salvage pathway and are implicated in the viability of several pathogenic organisms. Its absence in humans makes them a promising drug target. In addition, although they are key analytical biocatalysts for screening modulators in relevant biomedical enzymes, such as sirtuins and poly-ADP-ribosyltransferases, no commercial sources are available. Surprisingly, the finding of an affordable source of nicotinamidase from metagenomic libraries is hindered by the absence of a suitable and fast screening method. In this manuscript, we describe the development of two new whole-cell methods using the chemical property of one of the products formed in the enzymatic reaction (pyrazinoic or NA) to form colored complexes with stable iron salts, such as ammonium ferrous sulfate or sodium nitroprusside (SNP). After optimization of the assay conditions, a fosmid polygenomic expression library obtained from deep-sea mesophilic bacteria was screened, discovering several positive clones with the ammonium ferrous sulfate method. Their quantitative rescreening with the SNP method allowed the finding of the first nicotinamidase with balanced catalytic efficiency toward NAM (nicotinamidase activity) and pyrazinamide (pyrazinamidase activity). Its biochemical characterization has also made possible the development of the first high-throughput whole-cell method for prescreening of new nicotinamidase inhibitors by the naked eye, saving time and costs in the design of future antimicrobial and antiparasitic agents.
authors.affiliation: Department of Biochemistry and Molecular Biology-A, Faculty of Biology, Regional Campus of International Excellence "Campus Mare Nostrum", University of Murcia Murcia, Spain.
authors.forename: Rubén
authors.initials: R
authors.lastname: Zapata-Pérez
authors.affiliation: Department of Biochemistry and Molecular Biology-A, Faculty of Biology, Regional Campus of International Excellence "Campus Mare Nostrum", University of Murcia Murcia, Spain.
authors.forename: Antonio G
authors.initials: AG
authors.lastname: García-Saura
authors.affiliation: Univ Brest, CNRS, Ifremer, UMR 6197-Laboratoire de Microbiologie des Environnements Extrêmes (LM2E), Institut Universitaire Européen de la Mer (IUEM) Plouzané, France.
authors.forename: Mohamed
authors.initials: M
authors.lastname: Jebbar
authors.affiliation: School of Biological Sciences, Bangor UniversityBangor, UK; Immanuel Kant Baltic Federal UniversityKaliningrad, Russia.
authors.forename: Peter N
authors.initials: PN
authors.lastname: Golyshin
authors.affiliation: Department of Biochemistry and Molecular Biology-A, Faculty of Biology, Regional Campus of International Excellence "Campus Mare Nostrum", University of MurciaMurcia, Spain; Murcia Biomedical Research InstituteMurcia, Spain.
authors.forename: Álvaro
authors.initials: Á
authors.lastname: Sánchez-Ferrer
keywords: amidohydrolases; functional screening; high-throughput screening assays; library; metagenome; nicotinamidase