NAD Kinase in Corn: Regulation by Far Red Light is Mediated by Ca2+ and Calmodulin |
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Authors: | Dieter Peter; Marm? Dieter |
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Institution: | 1Biochemical Institute, University of Freiburg Hermann Herder Strasse 7, D-7800 Freiburg, F.R.G.
2Institute of Biology III, University of Freiburg Sch?ndestrasse 1, D-7800 Freiburg, F.R.G
3G?decke Research Institute Mooswaldallee, 1-9, D-7800 Freiburg, F.R. |
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Abstract: | Far red light irradiation of intact corn seedlings (Zea maysL.) has neither an effect on the cellular distribution nor onthe Ca2+, calmodulin-dependence of the NAD kinase (EC 2.7.1.23
EC]
).The enzyme is located in the outer mitochondrial membrane andits activity is totally dependent on the presence of both Ca2+and calmodulin, independently of the illumination. In intactmitochondria and the presence of calmodulin the enzyme activityincreases linearly from 100 nM to 1 mM. At 100 µM Ca2+halfmaximal activation occurs at about 10 nM calmodulin. After solubilizationand purification by calmodulin-Sepharose chromatography theCa2+dependence of the enzyme changes. The activation reachesa plateau at about 100 µM Ca2+ and half maximal activationoccurs at about 6 µM Ca2+. On the other hand irradiationof intact corn seedlings as well as an increase of the cellularCa2+ concentration leads to an increase of NADP and a correspondingdecrease of NAD. Based on these data we suggest that the lighteffect on the NAD kinase activity is mediated by Ca2+ and calmodulin. (Received May 31, 1986; Accepted July 14, 1986) |
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