The adenylation domain of the enzyme catalyses the activation of L-threonine to (L-threonyl)adenylate, followed by the transfer of the activated compound to the free thiol of a phosphopantetheine arm of a peptidyl-carrier protein domain. The peptidyl-carrier protein domain may be part of the same protein (as in the case of DhbF in bacillibactin biosynthesis), or of a different protein (as in the case of PmsD in pseudomonine biosynthesis). This activity is often found as part of a larger non-ribosomal peptide synthase.
