The role of phenylalanine hydroxylase in Parkinson's disease and amyotrophic lateral sclerosis

What is it about?

Background: The S-oxidation of S-carboxymethyl-L-cysteine has been reported previously to be a biomarker of disease susceptibility in Parkinson’s disease and amyotrophic lateral sclerosis. In the present investigation, the original observations have been extended and confirmed. Methods: Meta-analysis of previously published investigations into the S-oxidation polymorphism together with new subject data was evaluated. Results: The incidence of the poor metaboliser phenotype (no urinary recovery of S-oxide metabolites) was found to be 3%–7% within healthy and non-neurological disease populations, whereas 38% of the Parkinson’s disease subjects and 39% of the amyotrophic lateral sclerosis group were phenotyped as poor metabolisers. The consequent odds risk ratio of developing Parkinson’s disease was calculated to be 33.8 [95% confidence interval(CI), 13.3–86.1] and for amyotrophic lateral sclerosis was 35.2 (95% CI, 13.0–85.1). Conclusions: The possible involvement of the enzyme responsible for this S-oxidation biotransformation reaction,phenylalanine hydroxylase, should be further investigated to elucidate its potential role in the mechanism(s) of toxicity in susceptible individuals displaying these diseases. The “Janus hypothesis,” possibly explaining why phenylalanine hydroxylase is a biomarker of neurodegenerative disease susceptibility, together with the general theme that this concept may apply to many other hitherto unsuspected enzyme systems, is presented.

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Photo by freestocks.org on Unsplash

Photo by freestocks.org on Unsplash

Why is it important?

This publication is a land mark investigation into new biomarkers for Parkinson's disease and amyotrophic lateral sclerosis.