Impact of Sulfur Compounds on the Activity of Bacterial L-methioninase

The enzyme L-methioninase (EC 4.4.1.11) is present in all microbial species, while completely absent from mammals. This enzyme mainly catalyzes the α,γ-elimination of L-methionine, resulting in the production of α-ketobutyrate, methanethiol, and ammonia. The objective of this work was to achieve partly purification of L-methioninase from Staphylococcus sciuri. The enzyme was isolated and partially purified by the use of 80% ammonium sulfate precipitation. A range of concentrations (0.2, 0.4, 0.6, 0.8, and 1.0 mM) of four thiol compounds, namely cysteine, N-acetyl cysteine, thioglycolate, and glutathione, were examined in the reaction mixture to assess their impact on L-methioninase. Although all the substances examined exhibited enzyme activation at lower concentrations, higher concentrations functioned as inhibitors. Given that this enzyme is therapeutic, the results indicate that including the tested chemicals with its lower concentrations into the purified enzyme will improve its activity.