Trypsin-induced ATPase Activity in Potato Mitochondria

Area of Science:

• Plant biochemistry
• Mitochondrial function
• Enzyme regulation

Background:

• Mitochondria are key organelles for cellular respiration and energy production.
• ATPase activity is crucial for ATP hydrolysis and energy release.
• Potato mitochondria (Solanum tuberosum var. Russet Burbank) show low basal ATPase activity.

Purpose of the Study:

• To investigate the low ATPase activity in potato mitochondria.
• To identify factors regulating ATPase activity in plant mitochondria.
• To explore the potential presence of ATPase inhibitor proteins.

Main Methods:

• Mitochondrial isolation from Solanum tuberosum var. Russet Burbank.
• Assessing ATPase activity under various conditions (Mg2+, uncouplers, sonication, Triton X-100).
• Enzyme activity assays following treatment with trypsin, alkaline pH, and heat.

Main Results:

• Potato mitochondria displayed minimal ATPase activity, unresponsive to common activators or disruption methods.
• Trypsin treatment of disrupted potato mitochondria led to a 10- to 15-fold increase in Mg(2+)-dependent, oligomycin-sensitive ATPase activity.
• Similar trypsin-induced ATPase activation was observed in cauliflower, red sweet potato, and carrot mitochondria.
• Alkaline pH or heat treatment also activated ATPase in sonicated potato mitochondria.

Conclusions:

• Potato mitochondria possess a tightly associated ATPase inhibitor protein that masks basal activity.
• Proteolytic treatment (trypsin), alkaline pH, or heat can release or inactivate this inhibitor.
• The presence of an inhibitor protein regulating ATPase activity is a conserved feature in plant mitochondria.