title: Rapid screening for S-adenosylmethionine-dependent methylation products by enzyme-transferred isotope patterns analysis.
abstract: We report here an isotopic labeling and mass spectrometric method to rapidly identify S-adenosylmethionine (AdoMet)-dependent methylation products. In the presence of CH(3)- and CD(3)-labeled AdoMet, a methyl transfer product appears as a doublet separated by 3 Da in a mass spectrum, while other compounds show their normal isotopic distribution. Based on this unique isotopic pattern, methylation product(s) can be easily detected even from a mixture of cellular components. To validate our method, the product of human thiopurine methyltransferase (TPMT, EC 2.1.1.67) has been successfully identified from both an in vitro assay and a whole-cell assay. This method is generally applicable to AdoMet-dependent transmethylation and other group-transfer reactions, and constitutes the first example of a general strategy of enzyme-transferred isotope patterns (ETIPs) analysis.
authors.affiliation: Department of Chemistry, Washington State University, Pullman, WA 99164-4630, USA.
authors.forename: Wei
authors.initials: W
authors.lastname: Wan
authors.forename: Gang
authors.initials: G
authors.lastname: Zhao
authors.forename: Khalid
authors.initials: K
authors.lastname: Al-Saad
authors.forename: William F
authors.initials: WF
authors.lastname: Siems
authors.forename: Zhaohui Sunny
authors.initials: ZS
authors.lastname: Zhou
mesh_terms: D003903:Deuterium; D004926:Escherichia coli / Q000201:enzymology; D006801:Humans; D007553:Isotope Labeling; D008745:Methylation; D008780:Methyltransferases / Q000378:metabolism*; D012436:S-Adenosylmethionine / Q000032:analysis / Q000096:biosynthesis*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods*
chemical_list: D012436:S-Adenosylmethionine; D003903:Deuterium; D008780:Methyltransferases; C022745:thiopurine methyltransferase