Pristanic acid structure

Recent studies have led to a full resolution of the structure of the phytanic acid a-oxidation pathway. Indeed independent studies by Croes et aC and Verhoeven revealed that 2-hydrox5 hytanoyl-CoA undergoes cleavage to produce formyl-CoA and pristanal respectively, which is than oxidized to pristanic acid (Fig. 3B). The pristanic acid is now ready for p-oxidation after its activation to its CoA-ester. 

Figure 1 Fatty-acid structure and nomenclature. (A) Chemical formula and carbon atom numbering system for a 16-carbon saturated fatty acid (16 0). (B) Schematic representation of 16 0. (C) A monounsaturated fatty add, 18 1n-9, showing the double bond nine carbon atoms from the methyl end (carbon 18). (D) The essential n-6 fatty acid 18 2n-6, where the first double bond is found six carbon atoms from the methyl end. The two double bonds are separated by a methylene (-CH2-) group. (E) The essential n-3 fatty acid 18 3n-3, where the first double bond is found three carbon atoms from the methyl end. (F) Phytanic acid, a dietary / -methyl-branched-chain fatty acid (3,7,11,15-tetramethyl 16 0). The melhyl group on carbon 3 prevents this fatty acid from degradation by /3-oxidation. (G) Pristanic acid (2,6,10,14-tetramethyl 15 0) is the product of phytanic acid o-oxidation, in which a single carbon (carbon 1) is lost. The methyl group on carbon 2 does not preclude subsequent degradation by /3-oxidation.

Only a few major compound series can be recognized at the level of their molecular structures based on relative retention times and distribution patterns by gas chromatography alone. This applies to n-alkanes in the nonaromatic hydrocarbon fraction, n-fatty acids in the carboxylic acid fraction and in some cases n-alkanols in the neutral polar fraction. High abundance of a few single compounds (pristane, phytane, long-chain alkenones) sometimes also allow their direct identification from gas chromatograms. 

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