Effect of metals and phenylalanine on the activity of human tryptophan hydroxylase-2: comparison with that on tyrosine hydroxylase activity.

Department of Life Science, Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Yokohama 226-8501, Japan.

Neuroscience letters 2006 Jul 3

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We cloned the human tryptophan hydroxylase-2 (hTPH2) gene by RT-PCR, and expressed and purified its product as a maltose-binding protein (MBP)-fusion protein. We investigated the effects of essential divalent cations and L-phenylalanine (L-Phe) on the hTPH2 activity for the first time, and compared them with those on human tyrosine hydroxylase (hTH1) activity. We found that cobaltous and manganous ions inhibited the activities of both enzymes but that hTH1 was affected at lower concentrations than hTPH2. From kinetic analyses, we found that phenylalanine acted as an inhibitor more strongly against hTPH2 than against hTH1. These data are important for elucidating the molecular mechanism underlying the alterations in the contents of serotonin and catecholamines in the brain under pathological and physiological conditions, such as hyperphenylalaninemia and chronic manganese toxicity.

Citation

Shintaro Ogawa, Hiroshi Ichinose. Effect of metals and phenylalanine on the activity of human tryptophan hydroxylase-2: comparison with that on tyrosine hydroxylase activity. Neuroscience letters. 2006 Jul 3;401(3):261-5