Electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry to reveal the substrate specificity of the peptidyl-cysteine decarboxylase EpiD |
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Authors: | Schmid Dietmar G Majer Florian Kupke Thomas Jung Günther |
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Institution: | Institut für Organische Chemie, Universit?t Tübingen, Auf der Morgenstelle 18, 72076 Tübingen, Germany. |
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Abstract: | The microbial flavoenzyme EpiD catalyzes the oxidative decarboxylation of peptidyl-cysteines to peptidyl-aminoenethiols. These unusual C-terminally modified peptides are intermediates in the biosynthesis of the tetracyclic peptide antibiotic epidermin, which belongs to the lantibiotics family. The peptide SFNSYCC represents the C-terminal partial sequence of the natural precursor peptide EpiA. EpiA is posttranslationally modified to form finally the lantibiotic epidermin. The substrate specificity of EpiD was investigated using high-resolution mass spectrometry and the heptapeptide library SFNSXCC. The enzymatic conversion of particular peptides can be observed by a mass loss of m/z 46. In contrast to the previously used triple quadrupole instrument, electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI-FTICR-MS) was able to resolve and detect all precursor and converted peptides with identical nominal masses in a single measurement, avoiding the necessity to investigate single peptides. Furthermore, a new substrate SFNSCCC of the enzyme EpiD was detected within the reaction mixture. |
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