Ca2+-independent stimulation of cyclic GMP-dependent protein kinase by calmodulin |
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Authors: | T Yamaki H Hidaka |
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Institution: | Department of Pharmacology, Mie University, School of Medicine, Tsu 514, Japan |
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Abstract: | Calmodulin purified from bovine brain markedly stimulated cyclic GMP-dependent protein kinase from pig lung in the presence of cyclic GMP. This stimulation by calmodulin did not require Ca2+ and was dose-dependent up to optimal amounts, but the extent of stimulation decreased at concentrations over the optimal condition. The concentrations of cyclic GMP and cyclic AMP producing half-maximal stimulation were 4.5 × 10?8 M and 5.0 × 10?6 M respectively, under optimal conditions. Calmodulin increased maximum velocity without altering the Km for ATP. These effects of calmodulin on cyclic GMP-dependent protein kinase were similar to those of the stimulatory modulator described by Kuo and Kuo (J. Biol. Chem. , 4283–4286, 1976). Ouf findings indicate that calmodulin regulates enzyme activity both Ca2+-dependently and independently. |
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Keywords: | To whom all correspondence and reprint requests should be addressed |
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