Reaction: D-Ala-D-Ala + H2O = 2 D-Ala
Other name(s): D-alanyl-D-alanine dipeptidase; vanX D-Ala-D-Ala dipeptidase; VanX
Comments: A Zn2+-dependent enzyme [4]. The enzyme protects Enterococcus faecium from the antibiotic vancomycin, which can bind to the -D-Ala-D-Ala sequence at the C-terminus of the peptidoglycan pentapeptide (see diagram). This enzyme reduces the availability of the free dipeptide D-Ala-D-Ala, which is the precursor for this pentapeptide sequence, allowing D-Ala-(R)-lactate (for which vancomycin has much less affinity) to be added to the cell wall instead [2,3]. The enzyme is stereospecific, as L-Ala-L-Ala, D-Ala-L-Ala and L-Ala-D-Ala are not substrates [2]. Belongs in peptidase family M15.
Links to other databases: BRENDA, EXPASY, KEGG, MEROPS, Metacyc, CAS registry number:
References:
1. Reynolds, P.E., Depardieu, F., Dutka-Malen, S., Arthur, M. and Courvalin, P. Glycopeptide resistance mediated by enterococcal transposon Tn1546 requires production of VanX for hydrolysis of D-alanyl-D-alanine. Mol. Microbiol. 13 (1994) 1065-1070. [PMID: 7854121]
2. Wu, Z., Wright, G.D. and Walsh, C.T. Overexpression, purification, and characterization of VanX, a D-, D-dipeptidase which is essential for vancomycin resistance in Enterococcus faecium BM4147. Biochemistry 34 (1995) 2455-2463. [PMID: 7873524]
3. McCafferty, D.G., Lessard, I.A. and Walsh, C.T. Mutational analysis of potential zinc-binding residues in the active site of the enterococcal D-Ala-D-Ala dipeptidase VanX. Biochemistry 36 (1997) 10498-10505. [PMID: 9265630]
4. Bussiere, D.E., Pratt, S.D., Katz, L., Severin, J.M., Holzman, T. and Park, C.H. The structure of VanX reveals a novel amino-dipeptidase involved in mediating transposon-based vancomycin resistance. Mol. Cell. 2 (1998) 75-84. [PMID: 9702193]
5. Tan, A.L., Loke, P. and Sim, T.S. Molecular cloning and functional characterisation of VanX, a D-alanyl-D-alanine dipeptidase from Streptomyces coelicolor A3(2). Res. Microbiol. 153 (2002) 27-32. [PMID: 11881895]
6. Matthews, M.L., Periyannan, G., Hajdin, C., Sidgel, T.K., Bennett, B. and Crowder, M.W. Probing the reaction mechanism of the D-ala-D-ala dipeptidase, VanX, by using stopped-flow kinetic and rapid-freeze quench EPR studies on the Co(II)-substituted enzyme. J. Am. Chem. Soc. 128 (2006) 13050-13051. [PMID: 17017774]