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Publication date: 2009-09-30
Pol. J. Food Nutr. Sci. 2009;59(3):211-217
Glutamine deamidating enzyme from Penicillium politans NRC510 catalyzed deamidation of glutamine to glutamic acid and ammonia. The enzyme was partially purified by a simple methods of heating and Sephadex G-100 gel filtration. This procedure yields the partially purified enzyme with a 25% recovery of the activity in crude extracts. Specific activity of this partially purified enzyme is 133 U/mg. The partially purified enzyme hydrolyzes L-glutamine, D-glutamine L-asparagine and D-asparagine, while it cannot hydrolyze the other amide such as nicotinamide adenine dinucleotide, nicotinamide and acetamide under the same experimental conditions. The purified enzyme showed the maximal activity against L-glutamine at pH 7.5-8.5 and 60°C. The enzyme has a high salt tolerance, that shows high activity (75% of the original activity) in the presence of 15-30 % NaCl. Exposure of the partially purified enzyme to 60°C for 30 min in the absence of the substrate, has no effect on its activity. While it was inhibited to a variable extent by addition of some substances such as HgCl2, NaF, CaCl2, BaCl2 and CuSO4 but was not affected by 2-merceptoethanol and iodoacetate. Product inhibition was recorded by addition of glutamic acid or NH3 to the reaction mixture. Glutamic acid inhibition was a competitive type and the km and the ki values were found to be 7.5 and 39.0 mol/L, respectively.
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