Thiol-dependent degradation of protoporphyrin IX by plant peroxidases.
Protoporphyrin IX (PP) is the last porphyrin intermediate in common between heme and chlorophyll biosynthesis. This pigment normally does not accumulate in plants because its highly photodynamic nature makes it toxic. While the steps leading to heme and chlorophylls are well characterized, relatively little is known of the metabolic fate of excess PP in plants. We have discovered that plant peroxidases can rapidly degrade this pigment in the presence of thiol-containing substrates such as glutathione and cysteine. This thiol-dependent degradation of PP by horseradish peroxidase consumes oxygen and is inhibited by ascorbic acid.
Dayan
F E
FE
USDA/ARS Natural Products Utilization Research Unit, University, MS 38677, USA. fdayan@ag.gov
Rimando
A M
AM
Duke
S O
SO
Jacobs
N J
NJ
D001205:Ascorbic Acid / Q000494:pharmacology; D018553:Cucumis sativus / Q000378:metabolism*; D003545:Cysteine / Q000378:metabolism; D004791:Enzyme Inhibitors; D005978:Glutathione / Q000378:metabolism; D006735:Horseradish Peroxidase / Q000378:metabolism*; D007700:Kinetics; D010100:Oxygen / Q000378:metabolism; D018515:Plant Leaves / Q000201:enzymology*; D010940:Plant Proteins / Q000378:metabolism; D011524:Protoporphyrins / Q000378:metabolism*; D013438:Sulfhydryl Compounds / Q000378:metabolism*
D004791:Enzyme Inhibitors; D010940:Plant Proteins; D011524:Protoporphyrins; D013438:Sulfhydryl Compounds; C028025:protoporphyrin IX; D006735:Horseradish Peroxidase; D005978:Glutathione; D003545:Cysteine; D001205:Ascorbic Acid; D010100:Oxygen