A poly‐γ‐ d ‐glutamic acid depolymerase that degrades the protective capsule of B acillus anthracis

Summary A mixed culture of P seudomonas fluorescens and P usillimonas noertemanii , obtained by soil enrichment, elaborated an enzyme ( EnvD ) which rapidly hydrolysed poly‐γ‐ d ‐glutamic acid ( PDGA ), the constituent of the anti‐phagocytic capsule conferring virulence on B acillus anthracis . The EnvD gene is carried on the P . noertemanii genome but co‐culture is required for the elaboration of PDGA depolymerase activity. EnvD showed strong sequence homology to dienelactone hydrolases from other G ram‐negative bacteria, possessed no general protease activity but cleaved γ‐links in both d ‐ and l ‐glutamic acid‐containing polymers. The stability at 37° C was markedly superior to that of CapD , a γ‐glutamyltranspeptidase with PDGA depolymerase activity. Recombinant EnvD was recovered from inclusion bodies in soluble form from an E scherichia coli expression vector and the enzyme stripped the PDGA capsule from the surface of B . anthracis   P asteur within 5 min. We conclude from this in vitro study that rEnvD shows promise as a potential therapeutic for the treatment of anthrax.