O-methyltransferase CbzMT catalyzes iterative 3,4-dimethylations for carbazomycin biosynthesis

Area of Science:

• Natural Product Chemistry
• Microbial Biochemistry
• Enzymology

Background:

• Carbazomycins are carbazole derivatives with antifungal and antioxidant properties.
• Previous research lacked systematic biosynthetic studies on carbazomycins.
• The biosynthesis of these compounds remained largely uncharacterized.

Purpose of the Study:

• To elucidate the biosynthetic pathway of carbazomycins A and B.
• To identify and characterize the key enzymes involved in carbazomycin biosynthesis.
• To explore the potential for engineering biocatalysts for novel carbazomycin derivatives.

Main Methods:

• Isolation of carbazomycins A and B from *Streptomyces luteosporeus* using OSMAC screening.
• Identification of a biosynthetic gene cluster (BGC) and genetic manipulation of the *cbzMT* gene.
• Biochemical assays using size exclusion chromatography and *in vitro* enzyme activity tests.

Main Results:

• Carbazomycins A and B were successfully isolated and their biosynthetic gene cluster identified.
• Genetic manipulation of *cbzMT* confirmed its essential role in carbazomycin biosynthesis.
• *In vitro* studies revealed CbzMT acts as a dimer, catalyzing iterative methylations at C3 and C4 positions.

Conclusions:

• The study provides significant insights into carbazomycin biosynthesis, particularly the role of CbzMT.
• CbzMT's ability to perform iterative methylations expands the known repertoire of O-methyltransferases.
• These findings lay the groundwork for bioengineering novel carbazomycin analogs with enhanced bioactivity.