Modulation of Phosphoenolpyruvate Carboxylase Phosphorylation in Leaves of Amaranthus hypochondriacus,a NAD-ME Type of C4 Plant |
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Authors: | Parvathi K. Gayathri J. Maralihalli G.B. Bhagwat A.S. Raghavendra A.S. |
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Affiliation: | (1) Department of Plant Sciences, School of Life Sciences, University of Hyderabad, Hyderabad, 500 046, India;(2) Molecular Biology and Agriculture Division, Bhabha Atomic Research Center, Trombay, Mumbai, 400 085, India;(3) Department of Plant Sciences, School of Life Sciences, University of Hyderabad, Hyderabad, 500 046, India |
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Abstract: | PEP carboxylase (PEPC) in leaves of C4 plants is activated by phosphorylation of enzyme by a PEPC-protein kinase (PEPC-PK). We reevaluated the pattern of PEPC phosphorylation in leaf extracts of Amaranthus hypochondriacus. It was dependent on Ca2+, the optimum concentration of which for stimulation was 10 mM. The extent of stimulation was inhibited by 1,2-bis(2-aminophenoxy)ethane-N,N,N,N-tetraacetic acid (BAPTA), a Ca2+ chelator. The inhibition by BAPTA was relieved by the addition of Ca2+ but not by the addition of Mg2+. The stimulation by Ca2+ of PEPC phosphorylation was marginally enhanced by calmodulin (CaM), but not by diacylglycerol (DAG). Phosphorylation was strongly restricted by Ca2+ or Ca2+-CaM-dependent protein kinase inhibitors. Thus phosphorylation of PEPC is Ca2+-dependent in leaves of A. hypochondriacus and a calcium-dependent protein kinase (CDPK) may modulate PEPC-PK and subsequently the phosphorylation status of PEPC. |
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Keywords: | calcium calcium-dependent protein kinase PEPC-protein kinase |
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