1.3.1.118 phosphoprotein InhA is phosphorylated in vitro by multiple Ser/Thr kinases on residue Thr266.. Activity of InhA is controlled via phosphorylation. Thr266 is the unique kinase phosphoacceptor, both in vitro and in vivo. The physiological relevance of Thr266 phosphorylation is demonstrated using inhA phosphoablative (T266A) or phosphomimetic (T266D/E) mutants. Enoyl reductase activity is severely impaired in the mimetic mutants in vitro, as a consequence of a reduced binding affinity to NADH. Introduction of inhA_T266D/E fails to complement growth and mycolic acid defects of an inhA-thermosensitive Mycobacterium smegmatis strain, in a similar manner to what is observed following isoniazid treatment. Phosphorylation of InhA may represent an unusual mechanism that allows Mycobacterium tuberculosis to regulate its mycolic acid content, thus offering a new approach to future anti-tuberculosis drug development -, 748680