Phosphatidyltransferase activity in Bacillus megaterium.

Area of Science:

• Microbiology
• Biochemistry
• Enzymology

Background:

• Phosphatidyl transfer reactions are crucial in phospholipid metabolism.
• Bacillus megaterium is a model organism for studying bacterial membrane biogenesis.
• Cardiolipin synthase is a key enzyme in cardiolipin biosynthesis.

Purpose of the Study:

• To investigate phosphatidyl transfer activities in Bacillus megaterium membrane particles.
• To identify the enzyme responsible for catalyzing these transfer reactions.
• To compare the synthesis rates of different phospholipids.

Main Methods:

• Utilizing membrane particles from Bacillus megaterium strains ATCC 13632 and ATCC 14581.
• Assessing phosphatidyl transfer from various donors (phosphatidylethanolamine, phosphatidylglycerol, phosphatidylserine) to hydroxyl acceptors.
• Analyzing cardiolipin synthesis rates under different conditions (pH, heat, Triton X-100).

Main Results:

• Membrane particles catalyzed phosphatidyl transfer to ethanolamine, glycerol, serine, and Triton X-100.
• Cardiolipin synthesis from phosphatidylglycerol with ethanolamine was significantly faster than phosphatidylethanolamine formation.
• Cardiolipin synthesis from phosphatidylethanolamine with glycerol was also efficient.
• Similar heat lability, pH optima, and Triton X-100 sensitivity for phosphatidyl transfer and cardiolipin synthesis were observed.

Conclusions:

• Bacillus megaterium membrane particles possess phosphatidyl transferase activity.
• Cardiolipin synthase is the enzyme responsible for both phosphatidyl transfer and cardiolipin synthesis in these preparations.
• The enzyme exhibits distinct substrate preferences influencing phospholipid synthesis pathways.