Engineered Citrobacter freundii methionine γ-lyase effectively produces antimicrobial thiosulfinates

Area of Science:

• Biochemistry
• Enzymology
• Antimicrobial drug discovery

Background:

• Methionine γ-lyase (MGL) from Citrobacter freundii produces antimicrobial thiosulfinates.
• Enzyme engineering can enhance MGL's efficiency for novel antimicrobial applications.

Purpose of the Study:

• To engineer mutant forms of MGL to improve catalytic efficiency towards sulfoxides.
• To evaluate the antimicrobial activity of the engineered MGL in combination with sulfoxides.

Main Methods:

• Site-directed mutagenesis of MGL at the active site cysteine 115 (C115A, C115H).
• Assaying enzyme activity in γ-elimination and β-elimination reactions.
• Testing antibacterial activity of MGL-sulfoxide mixtures against Gram-positive and Gram-negative bacteria.

Main Results:

• C115H MGL mutant showed a tenfold increase in catalytic efficiency for β-elimination of S-substituted l-cysteine sulfoxides.
• The C115H MGL mutant lost activity in the γ-elimination reaction but retained β-elimination activity.
• Antibacterial activity was observed, with a more pronounced bacteriostatic effect against Gram-positive bacteria.

Conclusions:

• The mutant enzyme C115H MGL is an effective catalyst for sulfoxide decomposition.
• Pharmacological combinations of C115H MGL and sulfoxides represent promising new antimicrobial agents.