title: Reduction of aromatic L-amino acid decarboxylase activity in clonal pheochromocytoma PC12h cells by culture in the presence of N-methyl-4-phenylpyridinium ion (MPP+).
abstract: Rat clonal pheochromocytoma PC12h cells were cultured in the presence of N-methyl-4-phenylpyridinium ion (MPP+) and the activity of aromatic L-amino acid decarboxylase (AADC) was reduced after 3 and 6 days of culture. AADC activity in control cells was increased markedly by addition of pyridoxal 5-phosphate (PLP) to the reaction mixture, but that in the cells cultured in the presence of MPP+ was not increased by addition of PLP. After 6 days culture, AADC activity was almost negligible in the cells cultured in the presence of 1 mM MPP+, but PLP concentration in the cells was not reduced. AADC in the cells cultured in the presence of MPP+ reduced the affinity to PLP, but the affinity to a substrate, L-DOPA, did not change. Intracellular concentration of AADC protein was not reduced, as shown by an immunobinding assay with anti-AADC antibody. These data indicate that MPP+ may induce conformational changes in AADC protein and reduces its affinity to the cofactor, PLP.
authors.affiliation: Department of Biochemistry, Nagoya University School of Medicine, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Naoi
authors.forename: H
authors.initials: H
authors.lastname: Ichinose
authors.forename: T
authors.initials: T
authors.lastname: Takahashi
authors.forename: I
authors.initials: I
authors.lastname: Nagatsu
authors.forename: T
authors.initials: T
authors.lastname: Nagatsu
mesh_terms: D015655:1-Methyl-4-phenylpyridinium; D000818:Animals; D001142:Aromatic-L-Amino-Acid Decarboxylases / Q000378:metabolism*; D002452:Cell Count; D002460:Cell Line; D007980:Levodopa / Q000378:metabolism; D010673:Pheochromocytoma; D011726:Pyridinium Compounds / Q000494:pharmacology*; D051381:Rats; D012701:Serotonin / Q000378:metabolism; D014407:Tumor Cells, Cultured / Q000187:drug effects / Q000201:enzymology*
chemical_list: D011726:Pyridinium Compounds; D012701:Serotonin; D007980:Levodopa; D001142:Aromatic-L-Amino-Acid Decarboxylases; D015655:1-Methyl-4-phenylpyridinium