Human cathepsin X/Z is a biologically active homodimer

Area of Science:

• Biochemistry
• Molecular Biology
• Proteomics

Background:

• Human cathepsin X is a member of the lysosomal cysteine protease family.
• Understanding the structure and function of cathepsin X is crucial for elucidating its role in human diseases.

Purpose of the Study:

• To characterize the oligomeric state and biological activity of human cathepsin X.
• To investigate the potential implications of cathepsin X's structure on disease mechanisms.

Main Methods:

• Recombinant human procathepsin X was expressed in Pichia pastoris.
• Active cathepsin X was generated using aspartic cathepsin E.
• Size exclusion chromatography, X-ray crystallography, and small-angle X-ray scattering were employed for structural and biochemical analysis.

Main Results:

• Human cathepsin X was successfully expressed and activated in vitro.
• Structural analyses revealed that cathepsin X exists as a biologically active homodimer.
• The molecular weight of the cathepsin X homodimer was determined to be approximately 53 kDa.

Conclusions:

• Cathepsin X forms a homodimer, a novel finding that challenges previous assumptions.
• This dimeric structure may be critical for its enzymatic activity and biological function.
• The dimeric nature of cathepsin X opens new avenues for understanding its role in neurodegenerative disorders and other diseases.