Laccases derivatives

PCL and laccase derived from Myceliophthore (ML) were active for the polymerization of syringic acid to give PPO with molecular weight up to 1.8 x 104 [87]. Enzymatic synthesis of PPO was also achieved from 2,6-dimethylphenol using... 

Interestingly, an X-ray structure of a laccase derivative from Melanocarpus albomyces reveals what appears to be an O2 ligand spaced between all three T2/T3 copper ions (see Figure 14), although the Cu—O distances reported (2.4 to 2.6 A) are not in line with strong bonding interactions. 

Laccase (PCL) as well as peroxidases (HRP and SBP) induced a new type of oxidative polymerization of the 4-hydroxybenzoic acid derivatives, 3,5-dimethoxy-4-hydroxybenzoic acid (syringic acid) and 3,5-dimethyl-4-hydroxybenzoic acid. The polymerization involved elimination of carbon dioxide and hydrogen from the monomer to give PPO derivatives with molecular weight up to 1.8 x lO (Scheme 22). - ... 

Takahama, U. Oxidation of hydroxycinnamic acid and hydroxycinnamyl alcohol derivatives by laccase and peroxidase—interactions among p-hydroxyphenyl, guaiacyl and syringyl groups during the oxidation reactions. Physiol. Plantarum 1995, 93, 61-68. 

Kandelbauer A, Erlacher A, Cavaco-Paulo A, Guebitz GM (2004) Laccase catalyzed decolorization of the synthetic dye Diamond Black PV 200 and some structurally related derivatives. Biocatal Biotransformation 22 331-339... 

Camarero S, Ibarra D, Martinez MJ, Martinez AT (2005) Lignin-derived compounds as efficient laccase mediators for decolorization of different types of recalcitrant dyes. Appl Environ Microbiol 71(4) 1775-1784... 

Peroxidase and laccase enzymes were used to catalyze the decarboxylation of various tetrahydroisoquinoline-1-carboxylic acids to give high yields of the corresponding 3,4-dihydroisoquinolines (204). Compounds such as 125 (Scheme 29) are derived from Pictet-Spengler ring closure via a-keto acid and aryl amine condensation and are of biogenetic importance. The possible relevance of iso-... 

It should be noted that some commercial enzyme preparations may contain several enzyme isomers (enzymes derived from one source which belong to the same enzyme class but differ in specificity, stability or other properties). This is most often the case when the commercial preparation was developed for a process industry application rather than a specific chemical biotransformation application. Some fungal enzymes, such as laccase, are sometimes supplied as crude enzyme mixtures. Fungal laccases are manufactured on a huge scale (multitonne per annum) and are principally used in bulk processes such as wood... 

Three laccase preparations (I, II and III) were isolated from the racellular culture medium of Coriolus versicolor by consecutive fractionation through Sephadex G50 and DEAE Sephadex A25 (84). The laccase III preparation at pH 4.0 reduced the apparent molecular weight of a lignin-derived fraction that had been obtained by eluting the water-soluble extract of a cellulase treated ezomatsu wood residue through... 

Characterization of the Type 2 Depleted Derivative of Laccase. The model for the coupled blnuclear copper site in hemocyanln and tyrosinase (Figure 7) may now be compared to the parallel site in laccase which contains a blue copper (denoted Type 1 or Tl), a normal copper (Type 2, T2), and a coupled binuclear copper (Type 3, T3) center. As shown in Figures 8a and b, native laccase has contributions from both the Tl and T2 copper centers in the EPR spectrum (the T3 cupric ions are coupled and hence EPR nondetectable as in hemocyanln), and an intense absorption band at associated with the Tl center (a thlolate —> Cu(II) CT transition).(14) The only feature in the native laccase spectra believed to be associated with the T3 center was the absorption band at 330 nm (e 3200 M cm ) which reduced with two electrons, independent of the EPR signals.(15) Initial studies have focussed on the simplified Type 2 depleted (T2D) derlvatlve(16) in which the T2 center has been reversibly removed. From Figure 8 the T2 contribution is clearly eliminated from the EPR spectrum of T2D and the Tl contribution to both the EPR and absorption spectrum remains. 

When T2D laccase is reacted with peroxide the 330 nm band reappears (Figure 8a).(17) This observation suggested the possibility that the T3 site might be reduced in the T2D derivative but could be oxidized by 8202 Alternatively, other researchers assigned the 330 nm band as an Oj —> Cu(Il) charge transfer... 

Reduction of the met derivatives by one electron produces the mixed-valent 1/2-met (Cu(II)Cu(l)] derivatives. A comparison of the chemical and spectroscopic properties of 1/2-met hemocyanln and 1/2-met T2D laccase reveals a number of important differences (Figure 12). 

Figure 11. Comparison of EPR spectra of the uncoupled met derivatives of hemocyanln and T2D laccase with simulations for dipolar Interacting copper(II) s at distances Indicated. The peak Indicated by the asterisk results from subtraction of the T1 signal.

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