Proteolytic enzymes in normal and transformed cells.

Area of Science:

• Cell Biology
• Virology
• Biochemistry

Background:

• Virally transformed cells demonstrate increased proteolytic enzyme production.
• These enzymes may contribute to alterations in cell surface glycoproteins.
• The potential for membrane-bound proteases in transformed cells warrants investigation.

Purpose of the Study:

• To investigate the presence and localization of membrane-bound proteases in virally transformed cells.
• To compare protease activity in normal versus transformed cells.
• To identify specific proteases involved in viral transformation.

Main Methods:

• Comparative study of intact normal and transformed cells.
• Use of tritium-labeled protease inhibitor diisopropylfluorophosphate (DFP).
• Fibrinolytic assays to measure enzyme activity.

Main Results:

• Several proteases were identified and localized in the particulate cell fraction of transformed cells, suggesting they are membrane-bound.
• A DFP-reactive polypeptide of 62,000 molecular weight showed a 5-8 fold increase upon transformation.
• This polypeptide comigrated with fibrinolytic activity, indicating its enzymatic nature.
• Other particle-bound protease activities were also detected.

Conclusions:

• The study successfully identified and localized membrane-bound proteases in virally transformed cells.
• DFP-labeling in conjunction with fibrinolytic assays is a viable method for detecting these enzymes.
• The increased 62,000 MW polypeptide is a significant finding related to viral transformation.
• DFP labeling is useful for intracellular protease detection but lacks specificity for surface proteases.