Alteration of 1,2-diacylglycerol content in ischemic and reperfused heart |
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Authors: | Takahisa Kawai Kenji Okumura Hidekazu Hashimoto Takayuki Ito Tatsuo Satake |
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Institution: | (1) Laboratory of Biological Chemistry, University of Ioannina Medical School, P. O. Box 1186, GR-451 10 Ioannina, Greece;(2) Laboratory of Biological Chemistry, University of Ioannina Medical School, P.O. Box 1186, GR-451 10 Ioannina, Greece |
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Abstract: | Human term placenta contains an ATP diphosphohydrolase activity which hydrolyses ATP to ADP and inorganic phosphate and ADP to AMP and a second mole of inorganic phosphate. The activity has a pH optimum between 8.0 and 8.5. Magnesium or calcium ions are required for maximum activity. Other nucleoside phosphates, p-nitrophenyl phosphate or sodium pyrophosphate, are not hydrolysed. The activity is not due to ATPases, or to myokinase, as determined by the use of inhibitors. NaF and NaN3 were found to inhibit strongly the activity thus identifying it as an ATP diphosphohydrolase.A sensitive enzymatic assay for measurement of AMP, one of the products of the reaction, was established, based on the strong inhibition of muscle fructose 1,6-biphosphatase by AMP. The range of the assay was 0.05–0.8 µM AMP. ATP diphosphohydrolase was found to have a rate of AMP production from ADP twice the rate from ATP. Under the same conditions, the assay for Pi release, on the other hand, gave velocities similar to each other for the two substrates.The activity appears to be identical to the ADP-hydrolysing activity in placenta reported by others.Abbreviations Ap5A
P1
- P5-di(adenosine-5 )
Pentaphosphate
- ATP-DPH
ATP Diphosphohydrolase
- DCCD
N,N Dicyclohexycarbodiimide
- Fru-P2ase
Fructose 1,6-biphosphatase
- SDS
Sodium Dodecyl Sulfate
- TLC
Thin Layer Chromatography |
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Keywords: | ATP diphosphohydrolase apyrase human term placenta AMP assay |
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