Presence of ε‐adenosine tetraphosphate in chromaffin granules after transport of ε‐ATP
- 5 August 1996
- journal article
- Published by Wiley in FEBS Letters
- Vol. 391 (1-2) , 195-198
- https://doi.org/10.1016/0014-5793(96)00732-6
Abstract
Adenosine 5′‐tetraphosphate (Ap4) is a natural constituent of chromaffin granules with concentration values of 2.2±0.1 nmol/mg of protein and a ratio 245±40 times lower with respect to ATP (n=4). The granular transport of ε‐ATP resulted in a time‐ and concentration‐dependent production of ε‐adenosine tetraphosphate (ε‐Ap4) at the intragranular level. The ε‐Ap4 formation followed a hyperbolic saturation kinetic at low ε‐ATP concentrations with K m value of 0.4 μM ε‐ATP intragranular (1.15 pmol/mg of granular protein). Intragranular concentrations of ε‐ATP higher than 500 pmol/mg of protein (≈ 175 μM intragranular) resulted in a non‐saturable production of ε‐Ap4.Keywords
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