Isolation and characterization of an intracellular esterase from Lactobacillus casei subsp. casei IFPL731

An intracellular esterase from Lactobacillus casei subsp. casei IFPL731 was purified 1000-fold by ion exchange chromatography and gel filtration chrom atography. The relative molecular mass of the native enzyme was 105 kDa, wh ile the subunit molecular mass was estimated to be 38 kDa. The esterase hyd rolysed tributyrin and had a preference for esters of short-chain fatty aci ds (butyrate, caproate and caprylate), while it did not hydrolyse palmitate and sterate esters. The apparent Michaelis-Menten constant of the enzyme o n p-nitrophenyl butyrate was 0.3 mmol l(-1) while on p-nitrophenyl caprylat e, it was 0.04 mmol l(-1). The esterase was active over a broad range of pH and temperature values, and retained about 50% of maximal activity at pH 5 .0 and 12 degrees C. Activity was strongly inhibited by 5 mmol l(-1) phenyl methylsulphonyl fluoride, beta-mercaptoethanol and N-ethylmaleimide, and wa s stimulated by Zn2+ at 1 mmol l(-1).