Mycobacterium tuberculosis rv1400c encodes functional lipase/esterase

Area of Science:

• Biochemistry
• Enzymology
• Molecular Biology

Background:

• Lipases are crucial enzymes catalyzing triglyceride hydrolysis.
• The Mycobacterium tuberculosis genome contains numerous open reading frames (ORFs) encoding enzymes for fatty acid breakdown.
• The function of rv1400c, a putative Hormone Sensitive Lipase (HSL) subfamily ORF, was previously undefined.

Purpose of the Study:

• To define the enzymatic function of Mycobacterium tuberculosis rv1400c, designated LipI.
• To characterize the biochemical properties and catalytic activity of the purified LipI enzyme.
• To investigate the potential of M. tuberculosis LipI as a catalyst for polyunsaturated fatty acids.

Main Methods:

• Cloning, expression, and purification of rv1400c as a fusion protein in Escherichia coli.
• Enzyme activity assays using pNP-butyrate as a substrate to determine optimal conditions and specific activity.
• Site-directed mutagenesis to identify key catalytic residues (Ser165 and His291).
• Assessment of inhibition by SDS, CTAB, and Zn2+.

Main Results:

• Purified LipI exhibited optimal activity at 37°C and pH 8.0, with stability between pH 6.0 and 9.0.
• The enzyme showed a specific activity of 35.71 U/mg, preferring short-chain substrates like pNP-butyrate.
• Conserved residues Ser165 and His291 were identified as critical for catalytic activity.
• The enzyme's activity was inhibited by SDS, CTAB, and Zn2+.

Conclusions:

• M. tuberculosis LipI (rv1400c) is a functional lipase with specific biochemical characteristics.
• The enzyme demonstrates potential as a biocatalyst for polyunsaturated fatty acids.
• Further research into LipI could yield applications in fatty acid metabolism and biotechnology.