Mycobacterium tuberculosis VadK is required for the regulation of the methylcitrate cycle and virulence

The evolution of new enzymatic functions is constrained and guided by the architecture of an organism's metabolic and regulatory networks and environmental constraints. Here, we identify a kinase that has evolved from pyruvate phosphate dikinase. Using biochemical and systems-level analyses, we show that this enzyme, encoded by rv1127c in Mycobacterium tuberculosis (Mtb), has diverged from its ancestral role in central carbon metabolism to function as a histidine kinase in pathogenic mycobacteria and related species. We designate this enzyme Virulence Associated DiKinase (VadK), reflecting its ability to autophosphorylate and its role in virulence. VadK is essential for the utilization of carbon sources critical for survival within the host and to cause tuberculosis (TB) in murine models. Furthermore, VadK interacts with enzymes of the methylcitrate cycle, and ¹³C-tracer experiments demonstrates that it fine-tunes flux through this pathway, with elevated flux proving growth limiting. Together, these findings identify VadK as a regulatory kinase that integrates metabolic control with virulence in Mtb, revealing a new facet of metabolic regulation in bacterial pathogenesis and a potential target for therapeutic intervention.