InChI=1S/C20H40N4O10/c1-6(25)14-11(27)10(26)9(23)18(32-14)33-15-7(21)4-8(22)16(12(15)28)34-19-13(29)17(24-3)20(2,30)5-31-19/h6-19,24-30H,4-5,21-23H2,1-3H3/p+4/t6?,7-,8+,9+,10+,11-,12-,13+,14+,15+,16-,17+,18+,19+,20-/m0/s1 |
BRZYSWJRSDMWLG-CAXSIQPQSA-R |
C1[C@]([C@@H]([C@H]([C@H](O1)O[C@H]2[C@@H](C[C@@H]([C@H]([C@@H]2O)O[C@H]3O[C@@H]([C@H]([C@@H]([C@H]3[NH3+])O)O)C(O)C)[NH3+])[NH3+])O)[NH2+]C)(C)O |
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G418
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SUBMITTER
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geneticin
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UniProt
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CPD-14209
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MetaCyc accession
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View more database links |
Kim HJ, Liu YN, McCarty RM, Liu HW (2017) Reaction Catalyzed by GenK, a Cobalamin-Dependent Radical S-Adenosyl-l-methionine Methyltransferase in the Biosynthetic Pathway of Gentamicin, Proceeds with Retention of Configuration. Journal of the American Chemical Society 139, 16084-16087 (Source: SUBMITTER) [PubMed:29091410] [show Abstract] Many cobalamin (Cbl)-dependent radical S-adenosyl-l-methionine (SAM) methyltransferases have been identified through sequence alignment and/or genetic analysis; however, few have been studied in vitro. GenK is one such enzyme that catalyzes methylation of the 6'-carbon of gentamicin X2 (GenX2) to produce G418 during the biosynthesis of gentamicins. Reported herein, several alternative substrates and fluorinated substrate analogs were prepared to investigate the mechanism of methyl transfer from Cbl to the substrate as well as the substrate specificity of GenK. Experiments with deuterated substrates are also shown here to demonstrate that the 6'-pro-R-hydrogen atom of GenX2 is stereoselectively abstracted by the 5'-dAdo· radical and that methylation occurs with retention of configuration at C6'. Based on these observations, a model of GenK catalysis is proposed wherein free rotation of the radical-bearing carbon is prevented and the radical SAM machinery sits adjacent rather than opposite to the Me-Cbl cofactor with respect to the substrate in the enzyme active site. | Kim HJ, McCarty RM, Ogasawara Y, Liu YN, Mansoorabadi SO, LeVieux J, Liu HW (2013) GenK-catalyzed C-6' methylation in the biosynthesis of gentamicin: isolation and characterization of a cobalamin-dependent radical SAM enzyme. Journal of the American Chemical Society 135, 8093-8096 (Source: SUBMITTER) [PubMed:23679096] [show Abstract] The existence of cobalamin (Cbl)-dependent enzymes that are members of the radical S-adenosyl-l-methionine (SAM) superfamily was previously predicted on the basis of bioinformatic analysis. A number of these are Cbl-dependent methyltransferases, but the details surrounding their reaction mechanisms have remained unclear. In this report we demonstrate the in vitro activity of GenK, a Cbl-dependent radical SAM enzyme that methylates an unactivated sp(3) carbon during the biosynthesis of gentamicin, an aminoglycoside antibiotic. Experiments to investigate the stoichiometry of the GenK reaction revealed that 1 equiv each of 5'-deoxyadenosine and S-adenosyl-homocysteine are produced for each methylation reaction catalyzed by GenK. Furthermore, isotope-labeling experiments demonstrate that the S-methyl group from SAM is transferred to Cbl and the aminoglycoside product during the course of the reaction. On the basis of these results, one mechanistic possibility for the GenK reaction can be ruled out, and further questions regarding the mechanisms of Cbl-dependent radical SAM methyltransferases, in general, are discussed. |
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