Capsule-Targeting Depolymerase, Derived from Klebsiella KP36 Phage, As a Tool for the Development of Anti-Virulent Strategy

The rise of antibiotic-resistant , a leading nosocomial pathogen, prompts the need for alternative therapies. We have identified and characterized a novel depolymerase enzyme encoded by phage KP36 (depoKP36), from the family. To gain insights into the catalytic and structural features of depoKP36, we have recombinantly produced this protein of 93.4 kDa and showed that it is able to hydrolyze a crude exopolysaccharide of a host. Using in vitro and in vivo assays, we found that depoKP36 was also effective against a native capsule of clinical strains, representing the K63 type, and significantly inhibited -induced mortality of larvae in a time-dependent manner. DepoKP36 did not affect the antibiotic susceptibility of strains. The activity of this enzyme was retained in a broad range of pH values (4.0-7.0) and temperatures (up to 45 °C). Consistently, the circular dichroism (CD) spectroscopy revealed a highly stability with melting transition temperature (T) = 65 °C. In contrast to other phage tailspike proteins, this enzyme was susceptible to sodium dodecyl sulfate (SDS) denaturation and proteolytic cleavage. The structural studies in solution showed a trimeric arrangement with a high β-sheet content. Our findings identify depoKP36 as a suitable candidate for the development of new treatments for infections.