Abstract: The invention concerns a biosynthesis of nonaramatic polyketide compounds. More particularly, the present invention relates to a isolated polynucleotide molecule, a nucleic acid vector comprising the molecule, and isolated polypeptide and uses thereof. A new, type II thioestrerase can be obtained as an application outcome of this invention. The enzyme is active in polyketide, especially macrolide, biosynthesis when associated with a multienzyme complex of a polyketide synthase. The activity of the enzyme results in a increase of polyketide biosynthesis efficiency.