In silico analysis of the conformational changes of cefamandole inside and outside the active site of the β-lactamase k73a from mycobacterium tuberculosis

Experimentally it is not possible to calculate the energy nor the structure of the substrate during an enzymatic reaction. With the aid of in silico analysis, it is possible to follow the energetic and structural change of the conformers (products and substrates) that are involved in an enzymatic reaction. In the present work, an in silico analysis of the Cefamandole’s structural and energetic change was conducted; both, inside and outside the active site of the β-lactamase K73A fromMycobacterium tuberculosis. The energy for each conformer was determined by molcular mechanics. Cefamandole’s non-hydrolyzed energy, before entering the active site of β-lactamase K73A, was of 333.16 kJ/mol; inside the active site the value changed to 342.06 kJ/mol. The energy of the hydrolyzed Cefamandole inside the active site was of 323.86 kJ/mol; while outside of the active site the energy was 321.76 kJ/mol. The energy surge of the non-hydrolyzed Cefamandole inside the active site is due to a conformational change required to occupy the active site. The decrease in energy of the hydrolyzation makes the reaction irreversible. Hydrolyzed Cefamandole outside of the active site has the lowest energy, which explains the escape from the active site.