PURIFICATION, CRYSTALLIZATION AND CHARACTERIZATION OF N-ACETYLNEURAMINATE LYASE FROM ESCHERICHIA-COLI

N-Acetylneuraminate lyase produced by Escherichia coli was purified and crystallized from a genetically engineered strain (E. coli SF8/pNAL1). The enzyme showed apparent molecular masses of 105 000 Da on gel filtration and 35 000 Da on SDS/PAGE, suggesting that the enzyme is a trimer. The apparent optimum pH and temperature were found to be 6.5-7.0 and 80-degrees-C respectively. The K(m) values for N-acetylneuraminate and N-glycollylneuraminate were 3.3 and 3.3 mM respectively. The enzyme was inhibited by reduction with NaBH4 in the presence of the substrate, indicating that the enzyme belongs to the Schiff-base-forming Class I aldolases. The enzyme was strongly inhibited by Cu2+ ions, p-chloromercuribenzoate and N-bromosuccinimide, and also inhibited competitively by the reaction product, pyruvate, and its structurally related compounds, dihydroxyacetone and DL-glyceraldehyde.