Methylerythritol Phosphate Pathway: Enzymatic Evidence for a Rotation in the LytB/IspH‐Catalyzed Reaction

IspH/LytB, an oxygen‐sensitive [4Fe‐4S] enzyme, catalyzes the last step of the methylerythritol phosphate (MEP) pathway, a target for the development of new antimicrobial agents. This metalloenzyme converts (E)‐4‐hydroxy‐3‐methylbut‐2‐en‐1‐yl diphosphate (HMBPP) into the two isoprenoid precursors: isopentenyl diphosphate (IPP) and dimethylallyl diphosphate (DMAPP). Here, the synthesis of (S)‐[4‐2H1]HMBPP and (R)‐[4‐2H1]HMBPP is reported together with a detailed NMR analysis of the products formed after their respective incubation with E. coli IspH/LytB in the presence of the biological reduction system used by E. coli to reduce the [4Fe‐4S] center. (S)‐[4‐2H1]HMBPP was converted into [4‐2H1]DMAPP and (E)‐[4‐2H1]IPP, whereas (R)‐[4‐2H1]HMBPP yielded [4‐2H1]DMAPP and (Z)‐[4‐2H1]IPP, hence providing the direct enzymatic evidence that the mechanism catalyzed by IspH/LytB involves a rotation of the CH2OH group of the substrate to display it away from the [4Fe‐4S]. A reductive dehydroxylation is catalyzed by IspH/LytB, a [4Fe‐4S] enzyme target for the development of innovative antibacterial agents. The missing enzymatic evidence in the investigation of a rotation of the CH2OH group of the substrate in the catalytic mechanism of this enzyme is provided after synthesis of deuterium‐labeled stereoisomers of the substrate followed by the analysis of the products by several NMR methodologies.