Penicillium politans glutaminase

fungal glutamine amidohydrolase

fungal glutaminase

glutaminase in filamentous fungi

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.