The formation of Met from KMTB. The pathway of polyamine synthesis and subsequent Met regeneration from MTA, as known from K. pneumoniae  and B. subtilis , is shown. Solid arrows represent steps that have been characterised in M. tuberculosis (present study and ). The conversion of KMTB to Met is shown at the top in bold. KIC = ketoisocaproate, KIV = ketoisovalerate, and KMV = ketomethylvalerate.