This family represents the N-terminal region of the D-alanine--D-alanine ligase enzyme EC:6.3.2.4 which is thought to be involved in substrate binding [2]. D-Alanine is one of the central molecules of the cross-linking step of peptidoglycan assembly. There are three enzymes involved in the D-alanine branch of peptidoglycan biosynthesis: the pyridoxal phosphate-dependent D-alanine racemase (Alr), the ATP-dependent D-alanine:D-alanine ligase (Ddl), and the ATP-dependent D-alanine:D-alanine-adding enzyme (MurF) [3]. This domain is structurally related to the PreATP-grasp domain.

1: D-alanine:D-alanine ligase: phosphonate and phosphinate intermediates with wild type and the Y216F mutant. Fan C, Park IS, Walsh CT, Knox JR; Biochemistry 1997;36:2531-2538. PMID:9054558

2: The molecular basis of vancomycin resistance in clinically relevant Enterococci: crystal structure of D-alanyl-D-lactate ligase (VanA). Roper DI, Huyton T, Vagin A, Dodson G; Proc Natl Acad Sci U S A 2000;97:8921-8925. PMID:10908650

3: Roles of Mycobacterium smegmatis D-alanine:D-alanine ligase and D-alanine racemase in the mechanisms of action of and resistance to the peptidoglycan inhibitor D-cycloserine. Feng Z, Barletta RG; Antimicrob Agents Chemother 2003;47:283-291. PMID:12499203