Purification and characterization of the VanB ligase associated with type B vancomycin resistance in Enterococcus faecalis V583.

Acquired resistance to glycopeptides in enterococci is associated with the production of D-Alanine:D-Alanine ligase-related proteins. The VanA protein associated with high-level vancomycin and teicoplanin resistance (VanA phenotype) synthesizes a new peptidoglycan precursor, D-alanine-D-lactate, that has reduced glycopeptide affinity. Production of a similar protein, VanB, is induced in strains that display variable levels of vancomycin resistance but remain susceptible to teicoplanin (VanB phenotype). This paper describes the over-production, purification and characterization of VanB. Comparison of kinetic parameters of the two Van enzymes suggests that differences in catalytic efficiency could account, at least in part, for the various levels of vancomycin resistance.