The purification and characterization of intracellular invertase obtained from pathogenic Escherichia coli

All the non-pathogenic strains of Escherichia coli tested failed to synthesize invertase. However, among the pathogenic E. coli, only 11% of them synthesized the enzyme. Invertase synthesis was best at pH 8.0, when the sole nitrogen source was peptone. The enzyme was induced by sucrose but repressed by glucose and fructose. The enzyme was partially purified by ammonium sulphate precipitation, followed by dialysis and gel permeation chromatography. The partially purified invertase possessed a molecular weight of 125,000 KD and an apparent km of approximately 2.94mM for sucrose. The enzyme was stimulated by Ca++ and Mg++, inhibited by Cu++, U++, IAA and exhibited optimum activity at pH 6.5 at 40 degrees C.