Evaluation of the holoenzyme content of aromatic L-amino acid decarboxylase in brain and liver tissues. |
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| Authors: | Y Kawasaki H Hayashi K Hatakeyama H Kagamiyama |
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| Institution: | Department of Medical Chemistry, Osaka Medical College, Japan. |
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| Abstract: | We have re-evaluated the content of the holo-form of aromatic L-amino acid decarboxylase in rat tissues. Aromatic L-amino acid decarboxylase was found to consume pyridoxal 5'-phosphate while it underwent decarboxylation-dependent transamination as a side reaction. We observed that the total dopamine formation was proportional to the amount of holoenzyme. Dopamine formation in a tissue extract, which was preincubated with pyridoxal 5'-phosphate, was compared with the same tissue sample but which was prepared without preincubation. Percentages of holo-form of aromatic L-amino acid decarboxylase obtained from such comparison were 78% for brain and 94% for liver tissues. These values were significantly higher than those reported earlier in which the decarboxylation-dependent transamination of the decarboxylase had been overlooked. |
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