title: Formation of indigo by recombinant mammalian cytochrome P450.
abstract: The development of bicistronic systems for coexpression of recombinant human cytochrome P450 enzymes (P450s) with their redox partner, NADPH-cytochrome P450 reductase (NPR), has enabled P450 activity to be reconstituted within bacterial cells. During expression of recombinant P450 2E1 and some other forms, we observed the formation of a blue pigment in bacterial cultures. The pigment was extracted from cultures and shown to comigrate with standard indigo on TLC. UV-visible spectroscopy and mass spectrometric analysis provided further support for identification of the pigment as indigo. Indigo is known to form following the spontaneous oxidation of 3-hydroxyindole. Accordingly, we speculated that indole, formed as a breakdown product of tryptophan in bacteria, was hydroxylated by the P450 system, leading to indigo formation. Bacterial membranes containing recombinant P450 2E1 and human NPR were incubated in vitro with indole and shown to catalyze formation of a blue pigment in a time- and cofactor-dependent manner. These studies suggest potential applications of mammalian P450 enzymes in industrial indigo production or in the development of novel colorimetric assays based on indole hydroxylation.
authors.affiliation: Department of Physiology and Pharmacology, University of Queensland, Brisbane, Queensland, 4072, Australia. gillam@plpk.uq.edu.au
authors.forename: E M
authors.initials: EM
authors.lastname: Gillam
authors.forename: A M
authors.initials: AM
authors.lastname: Aguinaldo
authors.forename: L M
authors.initials: LM
authors.lastname: Notley
authors.forename: D
authors.initials: D
authors.lastname: Kim
authors.forename: R G
authors.initials: RG
authors.lastname: Mundkowski
authors.forename: A A
authors.initials: AA
authors.lastname: Volkov
authors.forename: F H
authors.initials: FH
authors.lastname: Arnold
authors.forename: P
authors.initials: P
authors.lastname: Soucek
authors.forename: J J
authors.initials: JJ
authors.lastname: DeVoss
authors.forename: F P
authors.initials: FP
authors.lastname: Guengerich
mesh_terms: D019392:Cytochrome P-450 CYP2E1 / Q000235:genetics / Q000378:metabolism; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D005796:Genes; D006801:Humans; D066298:In Vitro Techniques; D007203:Indigo Carmine; D007211:Indoles / Q000378:metabolism*; D009251:NADPH-Ferrihemoprotein Reductase / Q000235:genetics / Q000378:metabolism; D010860:Pigments, Biological / Q000378:metabolism*; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D007211:Indoles; D010860:Pigments, Biological; D011994:Recombinant Proteins; C030374:indole; D003577:Cytochrome P-450 Enzyme System; D007203:Indigo Carmine; D019392:Cytochrome P-450 CYP2E1; D009251:NADPH-Ferrihemoprotein Reductase