The document discusses the α-oxidation pathway of phytanic acid, identifying pristanal as a key product resulting from the decarboxylation of 2-hydroxyphytanoyl-CoA. The study outlines the metabolic process in human liver that converts phytanoyl-CoA into pristanic acid, highlighting deficiencies that lead to Refsum's disease. It also details the methods of analysis for pristanal and pristanic acid, emphasizing the enzymatic steps involved in their production and subsequent metabolism.

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
• For analysis of pristanal, ethoxylamine and 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.

9. Thank you for your attention