Developmental changes in the activity and substrate specificities of mouse brain monoamine oxidase |
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Authors: | Yayoi Koide Kiyofumi Kobayashi |
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Institution: | (1) Department of Clinical Neurochemistry Institute for Neurobiology, Okayama University Medical School, 2-5-1 Shikata-cho, 700 Okayama, Japan;(2) Present address: Department of Training Course for Nurse Teacher, Faculty of Teacher Education, Okayama University, 3-1-1 Naka, Tsushima, 700 Okayama, Japan |
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Abstract: | Developmental changes in monoamine oxidase (MAO) activity in the mouse brain were investigated with the substrates -phenylethylamine (PEA), tryptamine, and 5-hydroxytryptamine (5-HT). In the newborn brain, MAO activity towards PEA was found to be much lower than the adult and to be inhibited by clorgyline in a double-sigmoidal fashion. The inhibition curve shifted to a single-sigmoidal pattern with age. MAO activity towards 5-HT as substrate was inhibited by 90% and in a single-sigmoidal manner by clorgyline throughout the postnatal life. Lineweaver-Burk plots with PEA as substrate presented two linear lines (apparentK
m: 28.6 and 4.1 M) for the newborn and one line (apparentK
m: 11.4 M) for the adult, respectively. The plot with highK
m value for the newborn brain disappeared in a clorgyline-treated preparation. These findings suggest that age-dependent alterations in the ratio of MAO-A/MAO-B activity affect the substrate specificity of the enzyme. |
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