Phage Anti-Pycsar Proteins Efficiently Degrade β-Lactam Antibiotics

• Published in: Applied Biosciences 2024-10, Vol.3 (4), p.438-449
• Main Authors: Joshi, Pallav, Krco, Stefan, Davis, Samuel J., Asser, Lachlan, Brück, Thomas, Soo, Rochelle M., Bodén, Mikael, Hugenholtz, Philip, Wilson, Liam A., Schenk, Gerhard, Morris, Marc T.
• Format: Article
• Language: English
• Subjects: anti-Pycsar; antimicrobial resistance; carbapanemase; MBL-fold superfamily; metallo-beta-lactamase (MBL); virus
• ISSN: 2813-0464; 2813-0464
• DOI: 10.3390/applbiosci3040028

Metallo-β-lactamases (MBLs) are members of the structurally conserved but functionally diverse MBL-fold superfamily of metallohydrolases. MBLs are a major concern for global health care as they efficiently inactivate β-lactam antibiotics, including the “last-resort” carbapenems, and no clinically suitable inhibitors are currently available. Increasingly, promiscuous β-lactamase activity is also observed in other members of the superfamily, including from viruses, which represents an underexplored reservoir for future pathways to antibiotic resistance. Here, two such MBL-fold enzymes from Bacillus phages, the cyclic mononucleotide-degrading proteins ApycGoe3 and ApycGrass, are shown to degrade β-lactam substrates efficiently in vitro. In particular, ApycGrass displays a distinct preference for carbapenem substrates with a catalytic efficiency that is within one order of magnitude of the clinically relevant MBL NDM-1. Mutagenesis experiments also demonstrate that the loss of a metal-bridging aspartate residue reduces nuclease activity up to 35-fold but improves carbapenemase activity. In addition, we hypothesise that the oligomeric state significantly influences β-lactamase activity by modifying access to the active site pocket. Together, these observations hint at a possible new avenue of resistance via the spread of phage-borne MBL-fold enzymes with β-lactamase activity.