Copper-peptides mimicking catalytic activity of laccase in oxidation reactions
Laccase, an oxidative enzyme naturally found in fungi and bacteria, has been widely used in the fields of chemical and bio-catalysis. Its active site contains several copper ions making it very interesting for studies related to the structure and catalytic mechanisms. However, extracting laccase...
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| Main Author: | |
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| Format: | Thesis |
| Language: | English |
| Published: |
2020
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| Subjects: | |
| Online Access: | http://psasir.upm.edu.my/id/eprint/90718/1/FS%202020%2029%20IR.pdf |
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| Summary: | Laccase, an oxidative enzyme naturally found in fungi and bacteria, has been widely
used in the fields of chemical and bio-catalysis. Its active site contains several copper
ions making it very interesting for studies related to the structure and catalytic
mechanisms. However, extracting laccase uses large amounts of organic solvents to
attain low yield; making it a less preferred choice for all green chemistry applications.
The significance of this study is to mimic and enhance the catalytic activity of the
highest oxidation activity reported laccase from Trametes versicolor. The four peptide
sequences of the active sites found in most laccases was designed into nona (Np), hepta
(Hp), tetrapeptides (Tp1 and Tp2) using computational techniques. The peptides were
synthesized using Fmoc SPPS, analyzed and purified using HPLC and LC-MS.
Copper(II)-peptides identified as Np-CuC, Np-CuS, Np-CuN, Hp-CuC, Hp-CuS, Hp-
CuN, Tp1-CuC, Tp1-CuS, Tp2-CuC and Tp2-CuS were synthesized, crystallized and
analyzed using FTIR, Raman, NMR, AAS, XPS and CD. Different molar ratio of
peptides to copper(II) ions were analyzed for binding studies. These peptides and
copper-peptides were tested for their catalytic activity in oxidation reaction of benzyl
alcohol where both oxidation to benzaldehyde and disproportionation to toluene and
phenol were achieved simulataneously. Np-CuC was observed to have higher catalytic
activity (62.3%, 100% selectivity) than laccase (40.8%, 19.1% selectivity) towards
benzaldehyde. They were also used as catalysts in the degradation of twelve
pharmaceutical active compounds (PhACs). Tp2-CuS (1:2) proved to be a better
catalyst in the degradation of PhACs. Oxidation of 5-ASA and DCA catalyzed by these
copper peptides where Hp-CuS provided the highest yield of the oxidized product
(46.5%). These activities were compared with laccase (positive control) and no catalyst
(negative control). Overall, Np-CuC, Tp2-CuS and Hp-CuS were found to be better
catalysts for oxidation reactions compared to their parent peptides and laccase. |
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