Precursor-directed biosynthesis of 12-ethyl erythromycin

Area of Science:

• Biochemistry
• Synthetic Biology
• Natural Product Synthesis

Background:

• The erythromycin biosynthetic pathway offers potential for generating novel complex molecules.
• Previous work established precursor-directed biosynthesis for modifying the 6-deoxyerythronolide B (6-dEB) ethyl side chain (C14-C15).

Purpose of the Study:

• To extend precursor-directed biosynthesis for altering functionality at the C-12 position of 6-dEB.
• To generate novel 6-dEB derivatives and their corresponding erythromycin analogues.

Main Methods:

• Utilized an engineered mutant strain with altered 6-deoxyerythronolide B synthase (DEBS).
• Fed a designed synthetic substrate to the engineered strain to direct biosynthesis.
• Investigated the substrate's incorporation into 6-dEB and subsequent modification by tailoring enzymes.

Main Results:

• Successfully incorporated a designed substrate to yield a 6-dEB analogue with a 12-ethyl group.
• The 12-ethyl-6-dEB analogue served as a substrate for post-polyketide tailoring enzymes.
• Converted the 6-dEB analogue into the corresponding analogue of erythromycin C.

Conclusions:

• The precursor-directed biosynthesis method is effective for modifying the C-12 substituent of 6-dEB.
• Downstream tailoring enzymes tolerate the introduced unnatural 12-ethyl functionality.
• This approach, along with total biosynthesis via genetic engineering, can provide access to diverse erythromycin derivatives.