Phospholipid deacylating activities in murine leprosy bacilli

Area of Science:

• Microbiology
• Biochemistry
• Enzymology

Background:

• Leprosy is caused by Mycobacterium leprae, and understanding its cellular mechanisms is crucial for treatment.
• Mycobacterium lepraemurium, a related species, serves as a model for studying leprosy bacilli.
• Phospholipids are essential components of bacterial membranes, and their metabolism is vital for cell function.

Purpose of the Study:

• To investigate the phospholipid deacylating activities present in the particulate fraction of cultivated Mycobacterium lepraemurium.
• To characterize the substrate specificity and optimal conditions for these deacylating enzymes.
• To determine the influence of metal ions and detergents on enzyme activity.

Main Methods:

• Cultivation of Mycobacterium lepraemurium (Hawaiian-Ogawa strain).
• Preparation of particulate fractions for enzymatic assays.
• Hydrolysis assays using various phospholipid substrates (phosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol oligomannosides, 1-acyl-GPC, 2-acyl-GPC).
• Analysis of reaction products (fatty acids, lysophospholipids) using radiolabeled substrates.
• Assessment of the effects of pH, Ca2+, Triton X-100, Emulgen 913, and iron ions on enzyme activity.

Main Results:

• The particulate fraction exhibited phospholipid deacylating activities with acidic pH optima.
• Phosphatidylcholine and phosphatidylethanolamine were hydrolyzed at similar rates, while phosphatidylinositol oligomannosides were hydrolyzed more slowly.
• 1-acyl- and 2-acyl-GPCs were hydrolyzed more rapidly than phosphatidylcholine.
• Ca2+ did not stimulate enzyme activity.
• Triton X-100 and Emulgen 913 showed minimal effect on phosphatidylcholine hydrolysis but inhibited 1-acyl- and 2-acyl-GPC hydrolysis at high concentrations.
• Iron ions strongly inhibited phosphatidylcholine hydrolysis but had little effect on 1-acyl- and 2-acyl-GPC deacylation.
• Hydrolysis of radiolabeled phosphatidylcholine yielded both labeled fatty acid and lysophosphatidylcholine, with different labeling patterns observed for 1-acyl vs. 2-acyl isomers.

Conclusions:

• Mycobacterium lepraemurium possesses distinct phospholipid deacylating enzymes with specific substrate preferences and sensitivities to environmental factors.
• These enzymes play a role in the metabolism of key membrane phospholipids.
• The differential hydrolysis of various phospholipids and the influence of ions and detergents provide insights into the enzymatic machinery of Mycobacterium lepraemurium.