Effects of Calmodulin Antagonists on the Mitochondrial and Microsomal Ca2$ Uptake in Apple Fruit |
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Authors: | Fukumoto Masashi; Nagai Koushiro |
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Institution: | Morioka Branch, Fruit Tree Research Station, Ministry of Agriculture, Forestry and Fisheries Shimokuriyagawa, Morioka 020-01, Japan |
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Abstract: | In apple fruit, active ATP-dependent microsomal Ca2$ uptakeand respiration-dependent mitochondrial Ca2$ uptake were observed. The mitochondrial Ca2$ uptake was depressed by the calmodulinantagonists chlorpromazine hydrochloride (CPZ) and N-(6-aminohexyl)-5-chloro-1-naphthalene-sulfonamidehydrochloride (W-7). The Ca2$-ATPase from apple mitochondriawas also inhibited by CPZ or W-7. The apparent Km value forCa2$ in mitochondrial Ca2$ uptake (Km=0.35 mM) was similar tothat of mitochondrial Ca2$-ATPase (Km=0.32 mM). The inhibitoryeffect of W-7 on the activity of the mitochondrial Ca2$ uptakewas closely correlated with the inhibition by W-7 of mitochondrialCa2$-ATPase (r=0.996). These findings indicate that the mitochondrialuptake of Ca2$ in apple fruit depends on the calmodulin-mediatedactivation of Ca2$-ATPase. The microsomal Ca2$ uptake was depressed by CPZ, suggestingthat the microsomal Ca2$ uptake may also be modulated by calmodulin.
1 Contribution No. C-72, Fruit Tree Research Station. (Received June 7, 1982; Accepted October 19, 1982) |
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