Flux through Trehalose Synthase Flows from Trehalose to the Alpha Anomer of Maltose in Mycobacteria

SummaryTrehalose synthase (TreS) was thought to catalyze flux from maltose to trehalose, a precursor of essential trehalose mycolates in mycobacterial cell walls. However, we now show, using a genetic approach, that TreS is not required for trehalose biosynthesis in Mycobacterium smegmatis, whereas two alternative trehalose-biosynthetic pathways (OtsAB and TreYZ) are crucial. Consistent with this direction of flux, trehalose levels in Mycobacterium tuberculosis decreased when TreS was overexpressed. In addition, TreS was shown to interconvert the α anomer of maltose and trehalose using 1H and 19F-nuclear magnetic resonance spectroscopies using its normal substrates and deoxyfluoromaltose analogs, with the nonenzymatic mutarotation of α/β-maltose being slow. Therefore, flux through TreS in mycobacteria flows from trehalose to α-maltose, which is the appropriate anomer for maltose kinase of the GlgE α-glucan pathway, which in turn contributes to intracellular and/or capsular polysaccharide biosynthesis.

Graphical AbstractFigure optionsDownload high-quality image (244 K)Download as PowerPoint slideHighlights
► Flux through trehalose synthase (TreS) in mycobacteria is from trehalose to maltose
► The appropriate α anomer is formed by TreS for maltose kinase of the GlgE pathway
► The specificity of TreS for α-maltose is retained with deoxyfluoro analogs
► TreS supports cytosolic/capsular α-glucan but not trehalose mycolate biosynthesis