Phytanic and Pristanic Acid Are Naturally Occuring Ligands

Phytanic acid (3,7,11,15 tetramethylhexadecanoic acid) is an isoprenoid-derived 3-methyl fatty acid, which is solely derived from external sources. This branched-chain fatty acid originates from the phytol side chain of chlorophyll. Microorganisms, which are present in the rumen of ruminants, are thought to release phytol from chlorophyll, after which phytol is converted into phytanic acid (Patton and Benson, 1966). Because humans are not capable of phytol release from chlorophyll (Baxter, 1968), all phytanic acid enters the human body via the diet. Especially ruminant fats, fish and dairy products are rich sources of phytanic acid. Phytanic acid is metabolized into pristanic acid (2,6,10,14-tetramethylpentadecanoic acid) through a-oxidation. Degradation of pristanic acid starts with three cycles of P-oxidation in the peroxisome, followed by further s-oxidation in the mitochondrion (Verhoeven et al, 1998). Like phytanic acid, pristanic acid is present in lipids from many sources (Hansen, 1980).