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AIR2-CT93-1661
Structure, Function and Industrial Applications of Plant Laccases and Peroxidases |
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Contract No | AIR2-CT93-1661 |
| Total Cost | 1 688 790 | |
| EC Contribution | 1 542 982 | |
| Start Date | 01/01/1994 | |
| Duration | 60 months |
SUMMARY
Laccases and peroxidases are enzymes involved in the oxidation of phenolic compounds. Such compounds fill many roles in plants. They are constituents of lignin, provide pigmentation and are involved in a number of protective mechanisms including the response to wounding and viral infection. In the agro-food industry they are important as the major cause of biological colour in sugar and starch crops. The mechanisms of colour formation in paper pulping is also, in part, similar. In effect, the breaking of cells or cell walls releases both substrate and enzymes, resulting in coloured products. This project aims to obtain a better understanding of these enzymes through isolation, characterisation and expression in fermentation systems, as well as to look at potential applications in effluent decolorisation and other industrial applications such as enzyme-linked immunoassays.
OBJECTIVE
Task 1 is the purification and characterisation of specific isoenzymes of laccase and peroxidase, the cloning of the corresponding genes and a study of their expression. Enzymes studied will be:
(i) Arabidopsis peroxidase isoenzymes. Arabidopsis is an appropriate species as it is related to horseradish, traditionally the subject of peroxidase studies.
(ii) Xylem-specific isoperoxidases from poplar. This source is likely to be enriched in those isoenzymes principally involved in lignin biosynthesis.
(iii) Laccases from poplar and Arabidopsis.
Task 2 is a study of the catalytic properties of the purified isoenzymes. The results will provide information on the reactions catalysed so that the enzymes physiological roles and potential for exploitation can be assessed. Substrate specificity and reaction products will be determined. Spectroscopic thermodynamic and electrochemical studies will probe the catalytic mechanisms with special reference to copper centers.
Task 3 is the production of transgenic plants that over - or under - express specific isoperoxidases and laccases. Transformants with altered phenotype could be of value agriculturally and also for our basic understanding of the in-vivo roles of the enzymes. "Molecular farming" - the production of large amounts of specific isoenzymes in a stable form in the plants storage compartment - could be a valuable source of the interesting enzymes.
Task 4 is the testing of large quantities of specific laccases and peroxidases for industrial applications. The isoenzymes will be produced in bulk in microbial and/or higher plant heterologous systems. The ability of these enzymes to catalyse the degradation of aromatic pollutants in waste water and the decoloration of unwanted dyes, and their use in immunoassays will be explored. The stability of the enzymes under conditions encountered industrially will be tested. It is hoped that this work will allow European industry to exploit these two important but poorly understood enzymes.
Contacts
Coordinator
EC Scientific Officer
Participant
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