This is the N-terminal and middle domain found in Streptococcus pneumoniae peptidoglycan GlcNAc deacetylase (SpPgdA). PgdA protects the Gram-positive bacterial cell wall from host lysozymes by deacetylating peptidoglycan GlcNAc residues. It is a member of the family 4 carbohydrate esterases (CE-4) [1].

1: Structure and metal-dependent mechanism of peptidoglycan deacetylase, a streptococcal virulence factor. Blair DE, Schuttelkopf AW, MacRae JI, van Aalten DM; Proc Natl Acad Sci U S A. 2005;102:15429-15434. PMID:16221761