Bacterial collagenases involved in donor infection are widely applied in many fields due to their high activity and specificity; however, little is known regarding the mechanisms by which bacterial collagenases degrade insoluble collagen in host tissues. Using high-speed atomic force microscopy, we simultaneously visualized the hierarchical structure of collagen fibrils and the movement of a representative bacterial collagenase, Clostridium histolyticum type I collagenase (ColG), to determine the relationship between collagen structure and collagenase movement. Notably, ColG moved ~14.5 nm toward the collagen N terminus in ~3.8 s in a manner dependent on a catalytic zinc ion. While ColG was engaged, collagen molecules were not only degraded but also occasionally rearranged to thicken neighboring collagen fibrils. Importantly, we found a similarity of relationship between the enzyme-substrate interface structure and enzyme migration in collagen-collagenase and DNA-nuclease systems, which share a helical substrate structure, suggesting a common strategy in enzyme evolution.

Alzheimer's disease (AD) is the most prevalent age‐related neurodegenerative disorder, mainly characterized by amyloid β (Aβ) accumulation in the brain. Numerous new agents are currently undergoing clinical trials as disease‐modifying therapies (DMTs) targeting Aβ. ALZ‐801 is a promising candidate DMT for AD, with a phase 3 trial of ALZ‐801 ongoing specifically for apolipoprotein E (APOE) ε4 homozygous patients with early‐stage AD. This study aimed to examine the effects of ALZ‐801 on Aβ assembly and explore its toxicological profile. Thioflavin T (ThT) assays and two imaging modalities—transmission electron microscopy (TEM) and high‐speed atomic force microscopy (HS‐AFM)—were used to evaluate ALZ‐801's effects on Aβ assembly. To assess the effect of ALZ‐801 on Aβ ₄₂ ‐induced cytotoxicity, 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide (MTT) assays and lactate dehydrogenase (LDH) assays were performed. ThT assays revealed increased lag time and decreased fluorescence in the presence of ALZ‐801, confirming inhibition of Aβ ₄₂ fibril formation, as confirmed by TEM. Real‐time observation using HS‐AFM revealed that ALZ‐801 inhibited the formation of Aβ ₄₂ fibril from low‐molecular‐weight (LMW)‐Aβ ₄₂ in the presence of Aβ ₄₂ seeds. HS‐AFM also revealed that globular aggregates from LMW‐Aβ ₄₂ were significantly larger with ALZ‐801, with few fibrils noted. MTT and LDH assays indicated that ALZ‐801 prevented LMW‐Aβ ₄₂ ‐induced cytotoxicity but did not reduce cytotoxicity induced by high‐molecular‐weight‐Aβ ₄₂ . ALZ‐801 can inhibit Aβ ₄₂ aggregation by preventing both nucleus formation and fibril elongation, while promoting large globular oligomer formation, and can significantly reduce LMW‐Aβ ₄₂ ‐induced cytotoxicity. These findings underscore the potential of ALZ‐801 as an effective DMT for APOE ε4 homozygous patients with AD.