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 Va nA protein associated with high-level vancomycin and teicoplanin resis tance (VanA phenotype) synthesizes a new peptidoglycan precursor, D-al anine-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, purificati on and characterization of VanB. Comparison of kinetic parameters of t he two Van enzymes suggests that differences in catalytic efficiency c ould account, at least in part, for the various levels of vancomycin r esistance.