New insights have emerged about the geldanamycin amide synthase GdmF, pivotal for producing ansamycin antibiotics, shedding light on its catalytic mechanisms.
Researchers from various institutions have elucidated the role of GdmF, which catalyzes the formation of macrolactam rings from polyketide-derived seco-acids. This discovery is significant because geldanamycin, produced by Streptomyces hygroscopicus, is part of the ansamycin family of antibiotics, known for their ability to inhibit heat shock protein 90 (Hsp90), involved in cancer cell survival.
The study, published on March 13, 2025, revealed structural and functional characteristics of GdmF, which is important for developing new antibiotics, especially against resistant strains. The researchers managed to recombinantly express and purify GdmF and analyze its activity using synthetic substrates.
Crystallography allowed the team to visualize the ligand-free enzyme and its interactions with various substrate analogs. They discovered the presence of a catalytic triad consisting of cysteine, histidine, and aspartate, which facilitates the catalysis of macrolactam formation from the substrates. The study also showed how certain thioester groups interact within the enzyme’s active site.
During the kinetic assays, the research team measured the efficiency of GdmF with different substrates, demonstrating the enzyme’s broad substrate specificity. The kinetic parameters ranged from submillimolar to millimolar concentrations for maximum rates indicating the enzyme's varying catalytic efficiency.
Intriguingly, the structural analysis determined the flexibility of GdmF, particularly the interdomain region, which shifts during substrate binding. This flexibility may assist GdmF during the catalysis process, ensuring successful substrate interactions, and allowing for variable substrate lengths.
These findings represent the first detailed structural characterization of amide synthases and offer valuable insights on their catalytic mechanisms. Such knowledge could pave the way for the design of inhibitors targeting similar enzymes, potentially leading to new treatment options for antibiotic-resistant infections.
The potential for future applications stemming from this research is vast. It not only advances our fundamental scientific knowledge but also highlights important strategies for tackling one of modern medicine's most pressing challenges: antibiotic resistance.
Understanding enzymes like GdmF and their unique catalytic mechanisms will be integral to developing innovative antibiotics and therapeutic strategies, as scientists continue to search for ways to combat resilient pathogens.