Human cathepsin L, a papain-like collagenase without proline specificity

Area of Science:

• Biochemistry
• Enzymology
• Molecular Biology

Background:

• Papain-like peptidases can degrade collagen within its triple helix.
• Cathepsin K is a well-known human collagenase, typically cleaving substrates with proline at the P2 position.

Purpose of the Study:

• To investigate the collagenolytic activity of human cathepsin L, a close relative of cathepsin K.
• To compare the collagen cleavage patterns and affinities of cathepsin L and cathepsin K.
• To explore engineering cathepsin L for enhanced collagenolytic activity.

Main Methods:

• Assessing the collagenolytic activity of wild-type cathepsin L and cathepsin K on type I collagen.
• Comparing enzyme affinities and fragment release from insoluble and FITC-labeled collagen fibrils.
• Mutagenesis of cathepsin L active site residues (S2 subsite) to mimic cathepsin K.

Main Results:

• Cathepsin L efficiently cleaves type I collagen within the triple helix, producing a pattern similar to cathepsin K, despite lacking proline specificity.
• Both enzymes exhibit similar affinities for type I collagen and release proteolytic fragments.
• Mutating three residues in cathepsin L's S2 subsite conferred cathepsin K-like specificity and collagenolytic activity comparable to cathepsin K.

Conclusions:

• Cathepsin L possesses significant collagenolytic activity, comparable to cathepsin K.
• Specific active site modifications can engineer enhanced collagenolytic function in papain-like peptidases.
• These findings offer a foundation for designing novel collagen-degrading enzymes.