Differences in oscillation frequencies between two key enzymes of aromatic amino acid catabolism inEuglena:Circadian rhythmicity of tryptophan 2,3‐dioxygenase vs. predominance of ultradian periods in tyrosine aminotransferase

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Abstract
In Euglena gracilis Klebs, strain Z, two key enzymes of aromatic amino acid catabolism, tryptophan 2,3‐dioxygenase and tyrosine aminotransferase exhibit an entirely different chronobiological behaviour, indicating that the pathways of the respective amino acids are largely independent from a dynamical point of view. Tryptophan 2,3‐dioxygease exhibits a pronounced circadian rhythm, whereas, under same conditions, tyrosine aminotransferase oscillates predominantly with an ultradian period. This difference is seen both in LD 12:12 and LL. In tyrosine aminotransferase, circadian rhythmicity is normally either undetectable or only present as a weak trend; occasionally, the circadian and ultradian oscillations can attain similar amplitudes.