Functions of Type II Thioesterases in Bacterial Polyketide Biosynthesis

Many polyketides show biological activities and have thus been applied in clinics, as food additives, and in agriculture. Type II thioesterases (TEIIs) play an important role in polyketide biosynthesis. Most TEIIs belong to α/β-hydrolase family and usually contain a catalytic triad Ser-His-Asp. In polyketide biosynthesis, TEIIs can play an editing role by removal of aberrant non-extendable acyl units in elongation steps, a starter unit selection role by removal of unfavored starter acyl units in initiation steps, and a releasing role by removal of final product in termination steps. Complementation of TEIIs has been observed and applied.