Expanding the Substrate Scope of Nitrating Cytochrome P450 TxtE by Active Site Engineering of a Reductase Fusion

Rakesh Saroay, Gheorghe Doru Roiban, Lona M. Alkhalaf, Gregory L. Challis

Research output: Contribution to journalArticleResearchpeer-review

5 Citations (Scopus)


Aromatic nitration reactions are a cornerstone of organic chemistry, but are challenging to scale due to corrosive reagents and elevated temperatures. The cytochrome P450 TxtE nitrates the indole 4-position of l-tryptophan at room temperature using NO, O2 and NADPH, and has potential to be developed into a useful aromatic nitration biocatalyst. However, its narrow substrate scope (requiring both the α-amino acid and indole functionalities) have hindered this. Screening of an R59 mutant library of a TxtE-reductase fusion protein identified a variant (R59C) that nitrates tryptamine, which is not accepted by native TxtE. This variant exhibits a broader substrate scope than the wild type enzyme and is able to nitrate a range of tryptamine analogues, with significant alterations to the aromatic and aminoethyl moieties.

Original languageEnglish
Pages (from-to)2262-2265
Number of pages4
Issue number13
Publication statusPublished - 1 Jul 2021


  • Biocatalysis
  • Indole
  • Nitration
  • Protein Engineering

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