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The effect of IAA and NAD kinase in wheat coleoptile is mediated by Ca~(2+)/calmodulin complex

Li Xia, Wang Ningning, Wang Shufang, Zhu Liangji

Biochemistry and Molecular Biology Department of Nankai University.Tianjin 300071

Abstract

NAD kinase (NADK) catalyzes the only known biochemical reaction leading to the phosphorylation of NAD~(+) to form NADP~(+), which is a rate-limiting factor in many reactions in plants and plays a key role in the control of metabolism. Enhanced by calcium, exogenous IAA increased NADK activity in etiolated wheat coleoptile segments. LaCl_(3), a potent calcium ion channel blocker, could inhibit effectively the IAA-induced activity of NADK. The inhibitive effect of LaCl_(3) could be reversed by the calcium ionophore A23187. Calmodulin could activate in vitro the NADK purified by anion exchange chromatography from wheat coleoptile segments. LaCl_(3), however, almost completely abolished the IAA-induced increase in NADK-dependent calmodulin content in wheat coleoptile.

Key words: Wheat coleoptile;NAD kinase;Ca~(2+);Calmodulin

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Citing This Article：

Li Xia, Wang Ningning, Wang Shufang, Zhu Liangji. The effect of IAA and NAD kinase in wheat coleoptile is mediated by Ca~(2+)/calmodulin complex. Acta Physiol Sin 1999; 51 (4): (in Chinese with English abstract).