TY - JOUR
T1 - Estimation of cytoplasmic free Mg2+ levels and phosphorylation potentials in mung bean root tips by in vivo 31P NMR spectroscopy
AU - Yazaki, Yoshiaki
AU - Asukagawa, Norio
AU - Ishikawa, Yutaka
AU - Ohta, Eiji
AU - Sakata, Makoto
N1 - Funding Information:
We express our gratitude to Dr. Y. Nakamura of Tokyo Institute of Technology for his technical advice on the3IP NMR measurements, and Dr. K. Torimitsu of NTT Basic Research Laboratories for his helpful advice in our study. We wish to thank Prof. T. Kishi of Keio University for allowing us to use the atomic absorption spectrophotometer. This work was partly supported by a Grant-in-Aid for Scientific Research from the Ministry of Education, Science and Culture of Japan, and by grants from IBM Japan Limited and Ito Ham Food Incorporated.
PY - 1988/9
Y1 - 1988/9
N2 - The cytoplasmic [MgATP]/[ATP]free ratios, free Mg2+ concentrations, and phosphorylation potentials in mung bean [Vigna mungo (L.) Hepper] root tip cells were investigated by 31P nuclear magnetic resonance spectroscopy. 31P NMR spectra show well defined peaks due to G6P, cytoplasmic Pi, vacuolar Pi, ATP, UDP-glucose and nicotinamide adenine nucleotides. The concentrations of phosphorus metabolites were determined from quantitative 31P NMR spectra. The [MgATP]/[ATP]free ratio was 9.45. Accordingly, about 90% of the cytoplasmic ATP was complexed to Mg2+. Utilizing the dissociation constant (Kd) determined for MgATP, the cytoplasmic free Mg2+ concentration was estimated to be 0.4mM. The NMR-derived phosphorylation potential, [ATP]/([ADP][Pi]), was 960 M-1. The sodium azide treatment decreased the [ATP]/[ADP] ratio and the phosphorylation potential, and increased the [Mg2+]free. Metabolic inhibition may have been enhanced by an increase in [Mg2+free and a decrease in the free energy change for ATP hydrolysis, which resulted due to a decrease in the ATP level.
AB - The cytoplasmic [MgATP]/[ATP]free ratios, free Mg2+ concentrations, and phosphorylation potentials in mung bean [Vigna mungo (L.) Hepper] root tip cells were investigated by 31P nuclear magnetic resonance spectroscopy. 31P NMR spectra show well defined peaks due to G6P, cytoplasmic Pi, vacuolar Pi, ATP, UDP-glucose and nicotinamide adenine nucleotides. The concentrations of phosphorus metabolites were determined from quantitative 31P NMR spectra. The [MgATP]/[ATP]free ratio was 9.45. Accordingly, about 90% of the cytoplasmic ATP was complexed to Mg2+. Utilizing the dissociation constant (Kd) determined for MgATP, the cytoplasmic free Mg2+ concentration was estimated to be 0.4mM. The NMR-derived phosphorylation potential, [ATP]/([ADP][Pi]), was 960 M-1. The sodium azide treatment decreased the [ATP]/[ADP] ratio and the phosphorylation potential, and increased the [Mg2+]free. Metabolic inhibition may have been enhanced by an increase in [Mg2+free and a decrease in the free energy change for ATP hydrolysis, which resulted due to a decrease in the ATP level.
KW - 31P NMR
KW - ATP
KW - Free Mg2+
KW - MgATP
KW - Mung bean (Vigna mungo)
KW - Phosphorylation potential
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M3 - Article
AN - SCOPUS:0001674051
SN - 0032-0781
VL - 29
SP - 919
EP - 924
JO - Plant and Cell Physiology
JF - Plant and Cell Physiology
IS - 6
ER -