Protein and gene structure of a blue laccase from Pleurotus ostreatus

Abstract

A new laccase isoenzyme (POXA1b, where POX is phenol oxidase), produced by Pleurotus ostreatus in cultures supplemented with copper sulphate, has been purified and fully characterized. The main characteristics of this protein (molecular mass in native and denaturing conditions, pI and catalytic properties) are almost identical to the previously studied laccase POXA1w. However, POXA1b contains four copper atoms per molecule instead of one copper, two zinc and one iron atom per molecule of POXA1w. Furthermore, POXA1b shows an unusually high stability at alkaline pH. The gene and cDNA coding for POXA1b have been cloned and sequenced. The gene coding sequence contains 1599 bp, interrupted by 15 introns. Comparison of the structure of the poxa1b gene with the two previously studied P. ostreatus laccase genes (pox1 and poxc) suggests that these genes belong to two different subfamilies. The amino acid sequence of POXA1b deduced from the cDNA sequence has been almost completely verified by means of matrix-assisted laser desorption ionization MS. It has been demonstrated that three out of six putative glycosylation sites are post-translationally modified and the structure of the bound glycosidic moieties has been determined, whereas two other putative glycosylation sites are unmodified.

Enzyme Production by Solid Substrate Fermentation of Pleurotus ostreatus and Trametes versicolor on Tomato Pomace

“…Moreover, as shown in Fig. 6, native PAGE analysis of the laccase isoenzymes produced by P. ostreatus SSF revealed two more bands besides the three isoenzymes normally secreted in liquid cultures [18,24,[36][37][38]. The existence of these new isoenzymes is consistent with the multiplicity of P. ostreatus laccase genes [39,40].…”

Laccase isozymes from Ganoderma lucidum MDU-7: Isolation, characterization, catalytic properties and differential role during oxidative stress

“…Multiple isoforms of laccase have been reported depending on the fungal species and different environmental factors [11][12][13]. Many aromatic compounds and metals ion have been reported which regulate the production of differential laccase isozymes [14,15].…”

Essential Role of the N- and C-terminals of Laccase from Pleurotus florida on the Laccase Activity and Stability

“…The basidiomycete fungus P. ostreatus produces several laccases, including POXC, POXA1w, POXA1b, POXA3a, and POXA3b [12][13][14]. POXA1b is the most widely used isoform (GenBank accession number, AJ005018.1) because of its stability under alkaline conditions [14].…”

“…POXA1b is the most widely used isoform (GenBank accession number, AJ005018.1) because of its stability under alkaline conditions [14]. POXA1b has a relatively high specific activity, which is required for industrial applications.…”