2005 Volume 79 Issue 2 Pages 71-78
Poly-γ-glutamate (PGA) is an unusual polypeptide in which glutamate is polymerized via γ-amide linkages. PGA is produced by Bacillus strains, Natrialba aegyptiaca, and hydra. PGA, which is biodegradable and highly water-absorbent acidic polymer, is not attacked by proteases, evades mammalian immune defense mechanisms, binds Ca^<2+>, and serves as a cryoprotective material. PGA may physiologically function as an adaptation agent in various environments. Multifarious applications of PGA have been developed based on its function. PGA produced by Bacillus subtilis IFO 3336 contains a large amount of D-glutamate. D-Glutamate was formed from L-glutamate by glutamate racemase in this organism. Two kinds of glutamate racemase isozymes, Glr and YrpC, were found in B, subtilis IFO 3336, and Glr supplied D-glutamate for the PGA production. The pgsBCA genes encoding the membrane-associated PGA synthetase complex of B. subtilis IFO 3336 were isolated. The PgsBCA enzyme complex synthesized PGA in an amidoligation-like manner. The structure and function of the enzyme complex are also discussed.
