The enzyme is part of the biosynthetic pathway of phenolphthiocerol, a lipid that serves as a virulence factor of pathogenic mycobacteria. It catalyses the elongation of 4-hydroxybenzoate that is loaded on its acyl-carrier domain to form (4-hydroxyphenyl)alkanoate intermediates. The enzyme adds either 8 or 9 malonyl-CoA units, resulting in formation of 17-(4-hydroxyphenyl)heptadecanoate or 19-(4-hydroxyphenyl)nonadecanoate, respectively. As the enzyme lacks a thioesterase domain [1], the product remains loaded on the acyl-carrier domain at the end of catalysis, and has to be hydrolysed by an as-yet unknown mechanism.
