Update on the biochemistry of chlorophyll breakdown

Plant Mol Biol. 2013 Aug;82(6):505-17. doi: 10.1007/s11103-012-9940-z. Epub 2012 Jul 13.


In land plants, chlorophyll is broken down to colorless linear tetrapyrroles in a highly conserved multi-step pathway. The pathway is termed the 'PAO pathway', because the opening of the chlorine macrocycle present in chlorophyll catalyzed by pheophorbide a oxygenase (PAO), the key enzyme of the pathway, provides the characteristic structural basis found in all further downstream chlorophyll breakdown products. To date, most of the biochemical steps of the PAO pathway have been elucidated and genes encoding many of the chlorophyll catabolic enzymes been identified. This review summarizes the current knowledge on the biochemistry of the PAO pathway and provides insight into recent progress made in the field that indicates that the pathway is more complex than thought in the past.

Publication types

  • Research Support, Non-U.S. Gov't
  • Review

MeSH terms

  • Biochemical Phenomena*
  • Chlorophyll / chemistry
  • Chlorophyll / metabolism*
  • Fluorescence
  • Gene Expression Regulation, Plant
  • Oxygenases / metabolism
  • Plant Proteins / metabolism


  • Plant Proteins
  • Chlorophyll
  • Oxygenases
  • pheide a oxygenase