Identification of skatolyl hydroperoxide and its role in the peroxidase-catalysed oxidation of indol-3-yl acetic acid

Irina G. Gazarian, L. Mark Lagrimini, Fred A. Mellon, Michael J. Naldrett, Gillian A. Ashby, Roger N.F. Thorneley

Research output: Contribution to journalArticle

62 Scopus citations

Abstract

Indol-3-yl acetic acid (IAA, auxin) is a plant hormone whose degradation is a key determinant of plant growth and development. The first evidence for skatolyl hydroperoxide formation during the plant peroxidase-catalysed degradation of IAA has been obtained by electrospray MS. Skatolyl hydroperoxide degrades predominantly non-enzymically to oxindol-3-yl carbinol but in part enzymically into indol-3-yl methanol via a peroxidase cycle in which IAA acts as an electron donor. Skatolyl hydroperoxide is degradable by catalase. Horseradish peroxidase isoenzyme C (HRP-C) and anionic tobacco per-oxidase (TOP) exhibit differences in their mechanisms of reaction. The insensitivity of the HRP-C-catalysed reaction to catalase is ascribed to the formation of HRP-C Compound III at the initiation step and its subsequent role in radical propagation. This is in contrast with the TOP-catalysed process in which skatolyl hydroperoxide has a key role. Indol-3-yl aldehyde is produced not via the peroxidase cycle but by catalysis involving ferrous peroxidase, Because indol-3-yl aldehyde is one of the main IAA-derived products identified in planta, we conclude that ferrous peroxidases participate in IAA catalytic transformations in vivo. A general scheme for peroxidase-catalysed IAA oxidation is presented.

Original languageEnglish (US)
Pages (from-to)223-232
Number of pages10
JournalBiochemical Journal
Volume333
Issue number1
DOIs
StatePublished - Jul 1 1998

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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