Transglutaminase activity in normal and transformed cells.

Area of Science:

• Biochemistry
• Cell Biology
• Enzymology

Background:

• Transglutaminase (TG) enzymes play crucial roles in cellular processes.
• Altered enzyme activity is often observed in cellular transformation.
• Understanding TG activity in normal versus transformed cells is key to cell biology.

Purpose of the Study:

• To investigate and compare transglutaminase activity in normal and transformed cell systems.
• To determine the cellular localization and regulation of transglutaminase activity.
• To explore the relationship between transglutaminase and putrescine incorporation in different cell states.

Main Methods:

• Assessed transglutaminase activity in paired normal and transformed human, hamster, and mouse cell lines.
• Fractionated cell components to localize enzyme activity, particularly in the particulate fraction (105,000 X g).
• Measured putrescine incorporation rates and analyzed trypsin's effect on enzyme activity.

Main Results:

• Significantly reduced transglutaminase activity was observed in virus- and chemically-transformed cells compared to normal counterparts.
• The majority of transglutaminase activity was found in the particulate cellular fraction.
• Enzyme activity peaked in non-mitotic normal cells, and trypsin treatment increased activity independently of protein synthesis.

Conclusions:

• Transformed cells exhibit diminished transglutaminase activity, suggesting a role in oncogenesis.
• Cellular localization and regulation of transglutaminase are linked to cell cycle status and external stimuli.
• These findings highlight transglutaminase as a potential biomarker and therapeutic target in cancer research.