Abstract
5'-Nucleotidase was partially purified from chicken and rat heart by the similar procedure used for the purification of the cytosol 5'-nucleotidase from chicken and rat liver. Some kinetic properties of the enzymes from heart were similar to those of the cytosol 5'-nucleotidase from the liver.
The heart enzymes from both species were activated by ATP. When AMP was used as a substrate, the substrate-velocity plot of the chicken heart enzyme was sigmoidal (h=1.8). ATP at the concentration of 5 mM converted the curve into hyperbolic one and decreased s0.5 from 40 mM to 8 mM. The substrate-velocity plot of the rat heart enzyme with AMP was hyperbolic even in the absence of ATP. ATP at the concentration of 5 mM activated the enzyme by decreasing Km from 21 mM to 7 mM.
AMP-hydrolysing activity of these two enzyme preparations from cardiac tissue was markedly increased with the decrease in adenylate energy charge [(ATP + 0.5ADP)/(ATP + ADP + AMP)] in the physiological range. This suggests that the cytosol 5'-nucleotidase is important in production of a vasodilator, adenosine, from AMP during hypoxic condition of the heart.
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Itoh, R., Oka, J. & Ozasa, H. REGULATION OF THE CYTOSOL 5′-NUCLEOTIDASE OF THE HEART BY ADENYLATE ENERGY CHARGE: 93. Pediatr Res 19, 759 (1985). https://doi.org/10.1203/00006450-198507000-00113
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DOI: https://doi.org/10.1203/00006450-198507000-00113