RESUMO
A N-acetylneuraminate lyase gene (shnal) from Staphylococcus hominis was cloned into pET-28a and expressed in Escherichia coli BL21 (DE3) host cells. The recombinant enzyme was purified and characterized. It is a homotetrameric enzyme with the optimum pH at 8.0 for the cleavage direction and the optimum pH and temperature were 7.5 and 45 degrees C for the synthetic direction. The activity of ShNAL is stable when incubated at 45 degrees C for 2 h but decreased rapidly over 50 degrees C. ShNAL showed high stability in a wide range pH from 5.0 to 10.0 with the residual activity being > 70% when the enzyme was incubated in different buffers at 4 degrees C for 24 h. Its K(m) towards N-acetylneuraminic acid, pyruvate and ManNAc were (4.0 +/- 0.2) mmol/L, (35.1 +/- 3.2) mmol/L and (131.7 +/- 12.1) mmol/L, respectively. The k(cat)/K(m) value of Neu5Ac, ManNAc, and Pyr for ShNAL were 1.9 L/(mmol x s), 0.08 L/(mmol x s) and 0.08 L/(mmol x s), respectively.