page_title: Tylactone synthase
section_title: Structure and function
hierarchical_section_title: Tylactone synthase / Structure and function
caption_attribution_description: English: Each TYLS module is represented with domains and products indicated. Post-PKS processing to tylactone indicated.
context_page_description: Tylactone synthase or TYLS is a Type 1 polyketide synthase. TYLS is found in strains of Streptomyces fradiae and responsible for the synthesis of the macrolide ring, tylactone, the precursor of an antibiotic, tylosin. TYLS is composed of five large multi-functional proteins, TylGI-V. Each protein contains either one or two modules. Each module consists of a minimum of a Ketosynthase, an Acyltransferase, and an Acyl carrier protein but may also contain a Ketoreductase, Dehydrotase, and Enoyl Reductase for additional reduction reactions. The domains of TYLS have similar activity domains to those found in other Type I polyketide synthase such as 6-Deoxyerythronolide B synthase. The TYLS system also contains a loading module consisting of a ketosynthase‐like decarboxylase domain, an acyltransferase, and acyl carrier protein. The terminal Thioesterase terminates tylactone synthesis by cyclizing the macrolide ring. After the TYLS completes tylactone synthesis, the tylactone molecule is modified by oxidation at C-20 and C-23 and glycosylation of mycaminose, mycinose, and mycarose to produce tylosin.
caption: TYLS System by module with domains and products displayed. Tylactone post-PKS processing to Tylosin indicated. MX indicates module where X is module number.[9]
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