Laccase 1

Laccase is a copper-containing enzyme, 1,4-benzenediol oxidase , isolated from lacquer tree, Rhuse venifera and found in fungi and microorganisms which are eukaryotes, but recently they found the increase of laccase in prokaryotes of proteins with a specific feature of it in the family enzyme. Laccase is also found in gram positive and negative of bacteria like species living in extreme habitats.^{1, 2, 4} Laccases are multicopper oxidases of wide specificity that carry out one-electron oxidation of phenolic and related compounds, and reduce O₂ to water.1, 2 Laccases are polymeric and generally contain one each of type 1, type 2, type 3 copper centers per subunit, where the type 2 and type 3 are close together forming a trinuclear copper cluster and type 1 is monocopper site. The structure of the trinuclear copper site is similar to ascorbate oxidase's and this is the place where the reduction of molecular oxygen and release of water happens. There is a strong anti-ferromagnetical coupling between these copper which maintains a hydroxyl bridge.1 However, the type 1 copper atom in laccase is 3-coordinate ,trigonal planar and bound by one Cys and two His residues, but it lacks the axial ligand present in the Type 1 copper centre in ascorbate oxidase. The absence of the axial ligand is aeffecting the reduction potential of the metalloenzyme.^{1, 4, 5}

The easiest way to detect activity in Laccases is to use the spectrophotometer. Substrates that are commonly used with this method are ABTS, syringaldazine, 2,6-dimethoxyphenol, and dimethyl-p-phenylenediamine. In type 1, there is absorption of 611 nm in UV visible and this is where the substrate oxidation takes place. In type 2 copper no absorption can be seen under the visible spectrum and in EPR studies reveals the paramagnetic. And, in type 3 has electron absorption at 330 nm. This type is one of the other protein super families which has the Tyrs and haemocyanine.³

Laccases can be polymeric, and the enzymatically active form can be a dimer or trimer. Other laccases, such as ones produces by the fungus Pleurotus ostreatus, play a role in the degradation of lignin, and can therefore be included in the broad category of ligninases.

Laccases can also be used as the cathode in an enzyme catalyzed fuel cell. They can be paired with an electron mediator to facilitate electron transfer to a solid electrode wire. Laccase is one of the few oxidoreductases commercialized as industrial catalysts. The enzyme can be used for textile dyeing, wine cork making and many other environmental and industrial appliances.⁶

By looking at the structure of Laccase, we can find the point group of each copper and the symmetry of the whole structure. There is not a symmetry in this structure and we call it C₁. And, the point group is the collection of symmetry elements that satisfy the axioms of a mathematical group. The point groups of these three types of Coppers that I came up with it are as follow; type I Copper is C_2h, type II & III copper is C_3v. These three coppers are linked together as a pyramidal shape. We also can find the IR and Raman spectroscopy of the enzyme by finding the reducible representation of each copper by the formula and looking at the character table. In IR spectroscopy we see the changes of dipole moment. For finding the IR from character table, we look at the product function of the first column and see if each of the Mulliken symbols have X,Y,Z in front of it or not. In Raman spectroscopy we see the polarizability affects of electronic nature of chemical bonds in all direction. For finding the Raman spectroscopy, we look at the product of the symbols in the second column. For Copper type I which has the point group of C_2h, I found A₁+E for IR and Raman. And for Copper II and III which have the point group of C_3v, I found Au+Bu for IR and A_g+B_g for Raman.

Reference

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3. .Dedeyan, B, A Klonowska, S Tagger, T Tron, and G Iacazio. "Biochemical and MolecularCharacterization of a Laccase from Marasmius quercophilus." Applied andEnvironmental Microbiology 66.3 (2000): 925-929. Web. 24 May 2010.<http://aem.asm.org/cgi/content/full/66/3/925>.
4. Harald, C. "Laccase: structure, reactions, distribution." Micron (2004): 93-96. Web. 24 May 2010.<http://www.elsevier.com/locate/micron>.
5. Housecraft, C, and A Sharpe. Inorganic Chemistry. 3rd. Italy: Pearson Educational Limited, 2008.978- 980. Print.
6. "Laccase." Biotechnology 1. (2005): 38-50. Web. 23 May 2010.<http://www.bioportfolio.com/indepth/Laccase.html>.
7. "T.versicolor laccase." Web. 23 May 2010.<http://www.haraldkellner.com/assets/..._laccase3D.jpg>.