Purification and characterization of an erythromycin esterase from an erythromycin-resistant Pseudomonas sp.

An erythromycin esterase (molecular mass 51200 Da) was purified from Pseudomonas sp. GD100, which was isolated from a salmon hatchery sediment sample from Washington State. The pI of the protein was 4.5-4.8. The enzyme was inhibited by 1 mM mercuric acid, and had the substrate specificity for structurally related 14-membered macrolides, which decreased in the order of oleandomycin, erythromycin A and erythromycin A enol ether. The activity for erythromycin A varied with temperature, but the effect of pH was minimal at pH 6.0-9.0. The half-life of the enzyme was estimated to be 8.9 h at 35 degrees C and 0.23 h at 55 degrees C, and the activation energy of the catalytic reaction of erythromycin A was estimated at 16.2 kJ mol(-1).