Biosynthesis of TDP-l-mycarose: the specificity of a single enzyme governs the outcome of the pathway.
The biosynthetic pathway for l-mycarose, a 2,6-dideoxy-3-methylhexose found in the antibiotic tylosin produced by Streptomyces fradiae, has been studied with only two genes in the gene cluster, tylK and tylC2, remaining to be characterized. To verify the postulated functions of these two genes and to establish the sequence of events in the pathway, functional analyses of the proteins encoded by tylK and tylC2 were carried out. The results clearly show that TylK functions as the 5-epimerase and TylC2 functions as the 4-ketoreductase. However, both enzymes exhibit relaxed substrate specificity such that the production of TDP-l-mycarose as the sole product of the pathway depends on the absolute specificity of TylC3, a methyltransferase involved in an early step in the pathway. Exploitation of the promiscuous substrate specificity in the late steps of the mycarose pathway could produce new analogues of tylosin as well as other antibiotics containing this sugar.
Takahashi
Haruko
H
Division of Medicinal Chemistry, College of Pharmacy and Department of Chemistry and Biochemistry, University of Texas at Austin, Austin, Texas 78712, USA.
Liu
Yung-Nan
YN
Chen
Huawei
H
Liu
Hung-Wen
HW
D000900:Anti-Bacterial Agents / Q000096:biosynthesis* / Q000494:pharmacology; D001419:Bacteria / Q000201:enzymology / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D006601:Hexoses / Q000096:biosynthesis*; D008956:Models, Chemical; D010727:Phosphoric Diester Hydrolases / Q000096:biosynthesis*; D013379:Substrate Specificity
D000900:Anti-Bacterial Agents; D006601:Hexoses; C045835:mycarose; D010727:Phosphoric Diester Hydrolases; C498508:TDP1 protein, human