Functional Characterization of a Ketoreductase-Encoding Gene med-ORF12 Involved in the Formation of a Stereospecific Pyran Ring during the Biosynthesis of an Antitumor Antibiotic Medermycin

Abstract

Medermycin, a polyketide antibiotic, possesses strong bioactivity against a variety of tumors through a novel mechanism and is structurally featured with a pyran ring containing two chiral centers (3S and 15R). By far the biosynthetic origin of such enantiomerical conformations still remains obscure. In the present study, we reported the functional characterization of a proposed ketoreductase Med-ORF12 encoded by medermycin biosynthetic cluster and revealed its involvement in the stereochemical control at C3 center of medermycin. Firstly, bioinformatics analysis of Med-ORF12 suggested that it belongs to a group of stereospecific ketoreductases. Next, a Med-ORF12-deficient mutant was obtained and LC/MS measurements demonstrated that medermycin production was completely abolished in this mutant. Meanwhile, it was found that two shunt products were accumulated at the absence of Med-ORF12. Finally, the reintroduction of Med-ORF12 into this mutant could restore the production of medermycin. In a conclusion, these data supported that Med-ORF12 is essential for the biosynthesis of medermycin and performs its role as a stereospecifc ketoreductase in the tailoring steps of medermycin biosynthetic pathway.

A single‐domain small protein Med‐ORF10 regulates the production of antitumour agent medermycin in Streptomyces

“…Based on the results obtained above, we assumed that Med‐ORF10 regulates the biosynthesis of MED probably by controlling the expression level of structural genes in med gene cluster. med ‐ORF12 in med gene cluster encodes a stereospecific ketoreductase responsible for the conversion of the bicyclic intermediate into ( S )‐DNPA ( 4 ) in the pathway of MED (Li et al ., 2005; He et al ., 2015). As Med‐ORF10 deficiency can result in ( S )‐DNPA ( 4 ) accumulation (Fig.…”

“…AM‐7161 (AM‐7161) and sequenced. Most of med genes are functionally assigned to MED biosynthesis (Ichinose et al ., 2003; Li et al ., 2005; He et al ., 2015). However, some genes, including med‐ ORF10 encoding a small protein composed of 147 amino acid residues, have yet to be annotated (Fig.…”

Genome Mining of the Marine Actinomycete Streptomyces sp. DUT11 and Discovery of Tunicamycins as Anti-complement Agents

“…Medermycin is featured with a fused three-ring structure composed of a benzene ring, a quinone and a stereospecific pyran ring, and possesses significant antitumor activities against many types of cancer cells as well as antibacterial activity ( He et al, 2015 ; Lü et al, 2015 ). Our studies indicate that DUT11 is a promising producer of medermycin for drug discovery.…”

Biosynthesis of oxygen and nitrogen-containing heterocycles in polyketides

“…Whether the enzyme actively participates in the post-reduction steps is still in debate. It was proposed that dehydration takes place while the substrate is still bound in the active site, but it is also known that this and the analogous reaction in similar systems like medermycin ( 35 ) can occur spontaneously [ 27 , 30 ].…”