title: A semi-rational approach to engineering laccase enzymes.
abstract: In order to develop improved laccase-based bio-catalysts, semi-rational mutagenesis of the laccase POXA1b from Pleurotus ostreatus was performed through a combination of directed evolution with elements of rational enzyme modification. The R4 laccase was prepared by joining mutations of previously selected POXA1b random variants. An enhancement of stability features was thus obtained, making the novel enzyme R4 more appropriate as scaffold for directed evolution. A library of 1000 randomly mutated variants of R4 was prepared and screened for the ability of oxidising 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS). One of the variants selected (V148L) for improved activity was also proved to show higher stability than R4 at pH 5, and to retain its high stability at pH 7 and 10. In comparison with the POXA1b wild-type laccase, the semi-rational approach allowed us to develop a more efficient bio-catalyst, rising specific activity on ABTS up to around 5-fold. The new variant was also proved to be both more versatile and more durable than the wild-type enzyme, exhibiting higher activity in wide temperature and pH ranges and higher stability at acidic (t (1/2) at pH 5 = 35 days), neutral (t (1/2) at pH 7 = 38 days) and alkaline (t (1/2) at pH 10 = 62 days) pH values.
authors.affiliation: Department of Organic Chemistry and Biochemistry, University of Naples Federico II, Complesso Universitario Monte S. Angelo, via Cintia, 4, 80126, Naples, Italy.
authors.forename: Annalisa
authors.initials: A
authors.lastname: Miele
authors.forename: Paola
authors.initials: P
authors.lastname: Giardina
authors.forename: Eugenio
authors.initials: E
authors.lastname: Notomista
authors.forename: Alessandra
authors.initials: A
authors.lastname: Piscitelli
authors.forename: Giovanni
authors.initials: G
authors.lastname: Sannia
authors.forename: Vincenza
authors.initials: V
authors.lastname: Faraco
mesh_terms: D052160:Benzothiazoles / Q000378:metabolism; D019020:Directed Molecular Evolution / Q000379:methods*; D004795:Enzyme Stability / Q000235:genetics*; D004926:Escherichia coli; D042845:Laccase / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D008958:Models, Molecular; D050505:Mutant Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D020076:Pleurotus / Q000201:enzymology*; D012441:Saccharomyces cerevisiae; D013379:Substrate Specificity; D013451:Sulfonic Acids / Q000378:metabolism
chemical_list: D052160:Benzothiazoles; D050505:Mutant Proteins; D013451:Sulfonic Acids; C002502:2,2'-azino-di-(3-ethylbenzothiazoline)-6-sulfonic acid; D042845:Laccase
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