Cover Feature: Unveiling Two Consecutive Hydroxylations: Mechanisms of Aromatic Hydroxylations Catalyzed by Flavin‐Dependent Monooxygenases for the Biosynthesis of Actinorhodin and Related Antibiotics (ChemBioChem 5/2020)

The cover feature picture shows the biosynthetic pathway of actinorhodin (ACT), a polycyclic polyketide antibiotic pigmented with sky‐blue. The ACT monomer is derived from eight “chicks” of malonyl‐CoA by a series of tailoring steps including key stepwise dihydroxylations (black arrows) catalyzed by ActVA‐5 (green), the oxygenase component of the ActVA‐5/ActVB hydroxylase system. ActVA‐5 products can be autoxidized, but ActVB flavin reductase (pink), which supplies ActVA‐5 with a reduced cofactor, FMNH2, reduces quinone‐form shunt products to hydroquinone intermediates (red arrows). The tricyclic product is dimerized to generate the product “bluebird”, ACT. More information can be found in the communication by K. Ichinose et al. on page 623 in Issue 5, 2020 (DOI: 10.1002/cbic.201900490).