Immunochemical difference between cathepsin D and cathepsin E-like enzyme from rat spleen

Area of Science:

• Biochemistry
• Immunology
• Enzymology

Background:

• Acid proteinases, including cathepsin D, play crucial roles in cellular protein degradation.
• Understanding the immunological relationships between different cathepsin D forms and related enzymes is vital for their functional characterization.

Purpose of the Study:

• To examine the immunological properties of acid proteinases from rat spleen, specifically cathepsin D (major and minor forms) and a cathepsin E-like enzyme.
• To determine the immunological relatedness of rat spleen cathepsin D to cathepsin D found in other rat tissues.

Main Methods:

• Preparation of rabbit antiserum against rat spleen cathepsin D-I.
• Quantitative precipitation assays to measure enzyme activity inhibition.
• Immunodiffusion and immunoelectrophoresis to assess immunological identity and differences.

Main Results:

• The antiserum against cathepsin D-I quantitatively precipitated cathepsin D-I activity.
• The antiserum showed identical reactions with cathepsin D-II, indicating immunological identity but slight electrophoretic mobility differences.
• The cathepsin E-like enzyme was not affected by the antiserum, confirming it is immunologically distinct from cathepsin D.
• Rat spleen cathepsin D demonstrated immunological identity with cathepsin D from rat brain, thymus, lungs, heart, liver, kidneys, and adrenals.

Conclusions:

• Rat spleen cathepsin D (both major and minor forms) is immunologically identical to cathepsin D found in various other rat organs.
• The cathepsin E-like acid proteinase is immunologically distinct from cathepsin D.