Human liver homogenate was incubated to study the α-oxidation pathway of phytanic acid. Gas chromatography analysis identified pristanal as the product of the decarboxylation of 2-hydroxyphytanoyl-CoA. Pristanal was converted to pristanic acid in a NAD+-dependent reaction in human liver, demonstrating that pristanal is an intermediate in the production of pristanic acid from phytanoyl-CoA. Deficiencies in α-oxidation enzymes can lead to the accumulation of phytanic acid and cause Refsum's disease.
1. Resolution of the Phytanic Acid
𝛼-Oxidation pathway:
Identification of Pristanal as
product of the decarboxylation
of 2-Hydroxyphytanoyl-CoA
N. M. Verhoeven, D. S. M. Schor, H. J. ten Brink, R. J. A. Wanders, and C. Jakobs
Department of Clinical Chemistry, Free University Hospital, Amsterdam, The
Netherlands; and Departments of Clinical Chemistry and Pediatrics, University of
Amsterdam, Academic Medical Centre, Amsterdam, The Netherlands
2. • Phytanic cannot be
metabolized by 𝛽-oxidation
because of the methyl group
on the 3-Carbon.
• The product of 𝛼-oxidation is
pristanic acid
• Phytanoyl-CoA dioxygenase
deficiency in 𝛼-oxidation
leads to Refsum’s disease.
In this study, Pristanal is
produced from 2-
hydroxyphytanoyl-CoA
and undergoes NAD+
dependent oxidation to
produce Pristanic acid in
human liver is
considered.
3. Methods
• Homogenized human liver was incubation to produce
pristanic acid
• Each 200 𝜇l of NAD+ was added after 0, 10, 30, 60 and 120
minutes through incubation
• Dodecylaldehyde was added as internal standard.
• Then they were analyzed by gas chromatography (for
pristanal-ethoxime m/z 326 was monitored, for
dodecylaldehyde-ethoxime m/z 228 was monitor)
4. Mass fragmentogram of a standard solution containing pristanal-
ethoxime and dodecylaldehyde-ethoxime as internal standard
5. Mass fragmentogram of an extract from the incubation medium of human
liver homogenate incubated at t=0
6. Mass fragmentogram of an extract from the incubation medium of
human liver homogenate incubated at t=100
7. When NAD+ is added,
pristanal is absent and
pristanic acid is present
8. 1. Phytanic acid is first catalyzed by
phytanoyl- CoA ligase to form
Phytanoyl-CoA
2. Phytanoyl-CoA is hydrolyzed by
phytanoyl- CoA hydroxylase, in a
process using Fe2+, to yield 2-
hydroxyphytanoyl-CoA.
3. 2-hydroxyphytanoyl-CoA is cleaved
by a lyase type of enzyme to form
pristanal and formyl-CoA (in turn
later broken down into formate)
4. Pristanal is converted into pristanic
acid in a NAD+ dependent reaction
5. Pristanic acid is further metabolised
by peroxisomal 𝛽-oxidation.
