| Title |
Purification and Characterization of a New L-Methioninase from Solid Cultures of Aspergillus flavipes |
| Author |
Ashraf S. A. El-Sayed |
| Address |
Microbiology Department, Faculty of Science, Zagazig University, Zagazig 44519, Egypt |
| Bibliography |
Journal of Microbiology, 49(1),130-140, 2011,
|
| DOI |
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| Key Words |
L-methioninase, Aspergillus flavipes, solid state fermentation, PLP enzyme properties, cytotoxicity |
| Abstract |
L-Methioninase was purified to electrophoretic homogeneity from cultures of Aspergillus flavipes using anionexchange and gel filtration chromatography by 12.1 fold compared to the crude enzyme preparation. The purified enzyme had a molecular mass of 47 kDa under denaturing conditions and an isoelectric point
of 5.8 with no structural glycosyl residues. The enzyme had optimum activity at pH 7.8 and pH stability from 6.8-8.0 at 35°C. The enzyme appeared to be catalytically stable below 40°C. The enzyme activity was strongly inhibited by DL-propargylglycine, hydroxylamine, PMSF, 2-mercaptoethanol, Hg2+, Cu2+, and
Fe2+, with slight inhibition by Triton X-100. A. flavipes L-methioninase has a higher catalytic affinity towards L-methionine (Km, 6.5 mM and Kcat, 14.1 S-1) followed by a relative demethiolating activity to L-homocysteine (Km, 12 mM and Kcat, 9.3 S-1). The enzyme has two absorption maxima at 280 and 420 nm, typical of other PLP-enzymes. Apo-L-methioninase has the ability to reconstitute its structural catalytic
state completely upon addition of 0.15 mM PLP. L-Methioninase has neither an appreciable effect on liver function, platelet aggregation, nor hemolysis of human blood. The purified L-methioninase from solid cultures of A. flavipes displayed unique biochemical and catalytic properties over the currently applied Pseudomonad
enzyme. |
