Structural and functional studies of a Fusarium oxysporum cutinase with polyethylene terephthalate modification potential.
BACKGROUND
Cutinases are serine hydrolases that degrade cutin, a polyester of fatty acids that is the main component of plant cuticle. These biocatalysts have recently attracted increased biotechnological interest due to their potential to modify and degrade polyethylene terephthalate (PET), as well as other synthetic polymers.


METHODS
A cutinase from the mesophilic fungus Fusarium oxysporum, named FoCut5a, was expressed either in the cytoplasm or periplasm of Escherichia coli BL21. Its X-ray structure was determined to 1.9Å resolution using molecular replacement. The activity of the recombinant enzyme was tested on a variety of synthetic esters and polyester analogues.


RESULTS
The highest production of recombinant FoCut5a was achieved using periplasmic expression at 16°C. Its crystal structure is highly similar to previously determined Fusarium solani cutinase structure. However, a more detailed comparison of the surface properties and amino acid interactions revealed differences with potential impact on the biochemical properties of the two enzymes. FoCut5a showed maximum activity at 40°C and pH 8.0, while it was active on three p-nitrophenyl synthetic esters of aliphatic acids (C(2), C(4), C(12)), with the highest catalytic efficiency for the hydrolysis of the butyl ester. The recombinant cutinase was also found capable of hydrolyzing PET model substrates and synthetic polymers.


CONCLUSIONS
The present work is the first reported expression and crystal structure determination of a functional cutinase from the mesophilic fungus F. oxysporum with potential application in surface modification of PET synthetic polymers.


CONCLUSIONS
FoCut5a could be used as a biocatalyst in industrial applications for the environmentally-friendly treatment of synthetic polymers.
Biotechnology Laboratory, School of Chemical Engineering, National Technical University of Athens, 5 Iroon Polytechniou Str., Zografou Campus, Athens 15780, Greece; Department of Chemistry and Biotechnology, Swedish University of Agricultural Science, SE-75007 Uppsala, Sweden.
Maria
M
Dimarogona
Biotechnology Laboratory, School of Chemical Engineering, National Technical University of Athens, 5 Iroon Polytechniou Str., Zografou Campus, Athens 15780, Greece.
Efstratios
E
Nikolaivits
Biotechnology Laboratory, School of Chemical Engineering, National Technical University of Athens, 5 Iroon Polytechniou Str., Zografou Campus, Athens 15780, Greece.
Maria
M
Kanelli
Biochemical and Chemical Process Engineering, Division of Sustainable Process Engineering, Department of Civil, Environmental and Natural Resources Engineering, Luleå University of Technology, SE-97187 Luleå, Sweden.
Paul
P
Christakopoulos
Department of Chemistry and Biotechnology, Swedish University of Agricultural Science, SE-75007 Uppsala, Sweden.
Mats
M
Sandgren
Biotechnology Laboratory, School of Chemical Engineering, National Technical University of Athens, 5 Iroon Polytechniou Str., Zografou Campus, Athens 15780, Greece. Electronic address: vtopakas@chemeng.ntua.gr.
Evangelos
E
Topakas
D000595:Amino Acid Sequence; D002265:Carboxylic Ester Hydrolases / Q000737:chemistry* / Q000502:physiology; D002384:Catalysis; D005670:Fusarium / Q000201:enzymology*; D006863:Hydrogen-Ion Concentration; D008969:Molecular Sequence Data; D011093:Polyethylene Terephthalates / Q000378:metabolism*; D011994:Recombinant Proteins / Q000737:chemistry; D013696:Temperature
D011093:Polyethylene Terephthalates; D011994:Recombinant Proteins; D002265:Carboxylic Ester Hydrolases; C019952:cutinase
Crystal structure; Escherichia coli; Heterologous expression; PET modification; Serine esterase