Evaluation of the holoenzyme content of aromatic L-amino acid decarboxylase in brain and liver tissues.
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.
Kawasaki
Y
Y
Department of Medical Chemistry, Osaka Medical College, Japan.
Hayashi
H
H
Hatakeyama
K
K
Kagamiyama
H
H
D000818:Animals; D001051:Apoenzymes / Q000032:analysis; D001142:Aromatic-L-Amino-Acid Decarboxylases / Q000032:analysis* / Q000302:isolation & purification / Q000378:metabolism; D001921:Brain / Q000201:enzymology*; D007700:Kinetics; D008099:Liver / Q000201:enzymology*; D008433:Mathematics; D008954:Models, Biological; D051381:Rats; D011919:Rats, Inbred Strains
D001051:Apoenzymes; D001142:Aromatic-L-Amino-Acid Decarboxylases