title: An Engineered Version of Human PON2 Opens the Way to Understand the Role of Its Post-Translational Modifications in Modulating Catalytic Activity.
abstract: The human paraoxonase 2 (PON2) has been described as a highly specific lactonase hydrolysing the quorum sensing molecule N-(3-oxododecanoyl)-L-homoserine lactone (3OC12-HSL) and having secondary esterase but not phosphotriesterase activity, in contrast with the related enzymes PON1 and PON3. It has been suggested that PON2 enzyme activity is dependent on glycosylation and its N-terminal region has been recently demonstrated to be a transmembrane domain mediating association to membranes. In the present study we describe a mutated form of PON2, lacking the above N-terminal region, which has been further stabilized by the insertion of six amino acidic substitutions. The engineered version, hence forth called rPON2, has been over-expressed in E.coli, refolded from inclusion bodies and purified, yielding an enzyme with the same characteristics as the full length enzyme. Therefore the first conclusion of this work was that the catalytic activity is independent from the N-terminus and protein glycosylation. The kinetic characterization confirmed the primary activity on 3OC12-HSL; accordingly, in vitro experiments of inhibition of the biofilm formed by Pseudomonas aeruginosa (PAO1) have demonstrated that rPON2 is more effective than PON1. In addition, we observed small but significant activity against organophosphorothiotes pesticides, m-parathion, coumaphos and malathion.The availability of fair amount of active protein allowed to pinpoint, by mass-spectrometry, ubiquitination of Lys 168 induced in rPON2 by HeLa extract and to correlate such post-translational modification to the modulation of catalytic activity. A mutational analysis of the modified residue confirmed the result.
authors.affiliation: Institute of Protein Biochemistry, National Research Council, Via Pietro Castellino 111, 80131 Naples, Italy.
authors.forename: Luigi
authors.initials: L
authors.lastname: Mandrich
authors.affiliation: Institute of Protein Biochemistry, National Research Council, Via Pietro Castellino 111, 80131 Naples, Italy.
authors.forename: Mariangela
authors.initials: M
authors.lastname: Cerreta
authors.affiliation: Institute of Protein Biochemistry, National Research Council, Via Pietro Castellino 111, 80131 Naples, Italy.
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Manco
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D043303:Aryldialkylphosphatase / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D055162:Biocatalysis; D018441:Biofilms / Q000254:growth & development; D015153:Blotting, Western; D004795:Enzyme Stability; D004926:Escherichia coli / Q000235:genetics; D006367:HeLa Cells; D006801:Humans; D008239:Lysine / Q000235:genetics / Q000378:metabolism; D013058:Mass Spectrometry; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D010575:Pesticides / Q000378:metabolism; D011487:Protein Conformation; D015202:Protein Engineering / Q000379:methods; D011499:Protein Processing, Post-Translational; D011550:Pseudomonas aeruginosa / Q000378:metabolism / Q000502:physiology; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity; D013696:Temperature; D054875:Ubiquitination
chemical_list: D010575:Pesticides; D011994:Recombinant Proteins; D043303:Aryldialkylphosphatase; C468411:PON2 protein, human; D008239:Lysine