Kawase_2026_Biochim.Biophys.Acta.Proteins.Proteom__141185

Weak metal ion binding to enzymes is often necessary for enzyme function; however, its detection remains difficult. The catalytic efficiency of Cut190, a cutinase-like enzyme, is higher with the weak binder Ca(2+) than with the strong binder Mn(2+). Upon the introduction of a disulfide bond into Cut190, the enzyme was stabilized and effectively degraded polyethylene terephthalate. Notably, Ca(2+) binding to the stabilized Cut190 mutant remained weak and was necessary for its function. Here, we demonstrate that native mass spectrometry and electron spin resonance spectroscopy are effective methods for analyzing weak metal ion binding to enzymes.