The Role of Phytol Degradation in Chlorophyll and Tocopherol (Vitamin E) Metabolism

Abstract

The phytol degradation in the model plant Arabidopsis thaliana was studied. Phytol is the hydrophobic side of chlorophyll and is considered to be most abundant isoprenoid molecule in the biosphere. But the degradation of phytol in plants is largely elusive. <br /> To study the phytol degradation pathway in plants, phytol and phytol-related lipids, including phytenal, tocopherol, chlorophyll and fatty acid phytyl ester were analyzed in Arabidopsis thaliana mutants under nitrogen deprivation or phytol supplementation. Gas chromatography-mass spectrometry, high pressure liquid chromatography, Quadrupole-time of flight mass spectrometry and Quadrupole-ion trap mass spectrometry were used in biochemical analysis. Besides, the subcellular localization and enzymatic function of AtHPCL was studied. Chlorotic stress induced by nitrogen deprivation or phytol supplementation results in the increase of phytol and phytol-related lipids, including chlorophyll, phytenal, tocopherol and fatty acid phytyl ester in Arabidopsis thaliana hpcl and pahx mutants, not in the alpha-Dox1, alpha-Dox2 single mutants and alpha-Dox1-alpha-Dox2 double mutant. AtHPCL is localized to peroxisomes and indeed harbors 2-hydroxy-acyl-CoA lyase activity, which is dependent on TPP. <br /> To summarize, 1) AtHPCL is localized to peroxisomes; 2) AtHPCL has TPP-dependent 2-hydroxy-acyl-CoA lyase activity; 3) The phytol degradation in Arabidopsis thaliana requires PAHX and HPCL; 4) alphaDOX1 and alphaDOX2 do not participate in phytol degradation.