Isolation, Purification and Characterization of L,D-transpeptidase 2 from Mycobacterium tuberculosis

Area of Science:

• Biochemistry
• Microbiology
• Structural Biology

Background:

• * *Mycobacterium tuberculosis* L,D-transpeptidase 2 is essential for synthesizing nonclassical 3-3 peptidoglycan cross-links.
• * These cross-links confer resistance to penicillin antibiotics, posing a significant challenge in tuberculosis treatment.
• * Understanding the enzyme's function and stability is critical for developing new anti-TB strategies.

Purpose of the Study:

• * To optimize the cultivation, isolation, and purification of recombinant *M. tuberculosis* L,D-transpeptidase 2.
• * To investigate the factors affecting enzyme stability, particularly the oxidation of its catalytic cysteine residue.
• * To characterize the biochemical properties of the purified enzyme and a variant lacking domain A.

Main Methods:

• * Optimization of recombinant protein expression and purification protocols.
• * Biochemical assays to assess enzyme activity and stability.
• * Determination of kinetic parameters for nitrocefin transformation.

Main Results:

• * Optimized conditions for producing active recombinant L,D-transpeptidase 2.
• * Identified oxidation of the free SH groups of catalytic cysteine Cys354 as a major cause of enzyme inactivation during expression and storage.
• * Determined biochemical characteristics and kinetic constants for wild-type and domain A-lacking L,D-transpeptidase 2.

Conclusions:

• * L,D-transpeptidase 2 is a viable target for anti-tuberculosis drug development.
• * Preventing Cys354 oxidation is crucial for maintaining enzyme activity and stability.
• * Further studies on domain A's role could reveal new therapeutic avenues.