Properties of lactase produced by enteropathogenic Escherichia coli from diarrhoeic children.

The quantity of lactase produced by enteropathogenic Escherichia coli (EPEC) was significantly higher (P less than 0.01) than that produced by non-EPEC. The enzyme production was induced by lactose but repressed by glucose and galactose. The lactase from EPEC which was partially purified by ammonium sulphate precipitation and gel permeation chromatography had a molecular weight of 56 kD and apparent Km of approximately 2.78 mM for lactose. The lactase exhibited optimum activity at pH 7.0 at 40 degree C and was stimulated by Mg2+, Mn2+, Na+ and inhibited by Ba2+, Ca+, Cu2+, EDTA, iodo acetic acid (IAA) and Hg2+ and U2+ ions. The higher production of lactase by EPEC may be linked to its pathogenic role in childhood diarrhoea.