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Purification and Characterization of a New L-Methioninase from Solid Cultures of Aspergillus flavipes
Faculty
Science
Year:
2011
Type of Publication:
Article
Pages:
130-140
Authors:
El-Sayed, Ashraf S. A
DOI:
10.1007/s12275-011-0259-2
Journal:
JOURNAL OF MICROBIOLOGY MICROBIOLOGICAL SOCIETY KOREA
Volume:
49
Research Area:
Microbiology
ISSN
ISI:000287944400019
Keywords :
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 anion-exchange 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 degrees C. The enzyme appeared to be catalytically stable below 40 degrees C. The enzre activity was strongly inhibited by DL-propargylglycine, hydroxylamine, PMSF, 2-mercaptoethanol, Hg(2+), Cu(2+), and Fe(2+) 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 mu, typical of other PLP-enzymes. Apo-L-methioninase has the ability to reconstitute its structural catalytic state completely upon addition of 0.15 mM PIP. 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.
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