Characterization of Methyltransferase AlmCII in Chalcomycin Biosynthesis: The First TylF Family O‐Methyltransferase Works on a 4′‐Deoxysugar

Abstract

Sugar O-methylation is a ubiquitous modification in natural products and plays diverse roles. This realization has inspired many attempts to search for novel methyltransferases. Chalcomycins are a group of 16-membered macrolides containing two methylated sugars that require three methyltransferases for their biosynthesis. Here, we identified that AlmCII, a sugar O-methyltransferase belonging to the TylF family that was previously only known to methylate sugars with a 4'-hydroxy group, can methylate a 4',6'-dideoxysugar during the biosynthesis of chalcomycins. An in vitro enzymatic assay revealed that AlmCII is divalent metal-dependent with an optimal pH of 8.0 and optimal temperature of 42 °C. Moreover, the 3'-O-demethylated chalcomycins exhibit less than 6 % of the antibacterial activity of their parent compounds. This is the first report demonstrating that a TylF family O-methyltransferase can use a 4'-deoxy sugar as a substrate and highlighting the importance of this methylation for the antibacterial activity of chalcomycins.

Biosynthesis of clinically used antibiotic fusidic acid and identification of two short-chain dehydrogenase/reductases with converse stereoselectivity

“…Antibacterial activity of compounds 1 , 3 , 4 , and 5 against Gram-positive strain Staphylococcus aureus 209 P was evaluated using the 2-fold dilution assay17., 18., 19.. Seed cultures of S. aureus 209 P was inoculated on beef extract medium at 37 °C for 1 day.…”

Functional Characterization of a Regiospecific Sugar-O-Methyltransferase fromNocardia

“…The regiospecific chemical synthesis of O -methylated sugars is challenging and unsustainable because it requires (i) harsh catalytic conditions, (ii) the release of toxic by-products, (iii) a long reaction time, (iv) protection/deprotection of unwanted groups, and (v) expensive reagents. Nevertheless, biocatalytic methylation using enzymes and engineered microorganisms are capable of O -methylation of compounds for producing novel bioactive compounds in a much milder and single-step reaction using resources from microbial cells ( 26 , 27 ).…”

Biosynthetic Study of Cephalosporin P1 Reveals a Multifunctional P450 Enzyme and a Site-Selective Acetyltransferase

“…These compounds were tested for antimicrobial activity against Gram-positive Staphylococcus aureus 209P by the 2-fold dilution method. 22 Most of the compounds showed potent inhibitory activity (Table S3 in the Supporting Information). Among them, cephalosporin P 1 is the most active compound with a MIC value of 0.06 μg mL −1 .…”

“…By heterologous expression in A. oryzae , we obtained cephalosporin P 1 and 10 other analogues, including five new compounds. These compounds were tested for antimicrobial activity against Gram-positive Staphylococcus aureus 209P by the 2-fold dilution method . Most of the compounds showed potent inhibitory activity (Table S3 in the Supporting Information).…”