Measurement and kinetic study of the formation of adrenaline sulphate in vitro

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Abstract
The sulpho-conjugation of [14C]adrenaline form inorganic sulphate and ATP or preformed adenosine 3′-phosphate 5′-sulphatophosphate was demonstrated in the high-speed supernatant prepared from the liver and small intestine of various animals. Hydrolysis with sulphatase indicated the sulphate nature of the conjugate. The overall sulphation reaction has a pH optimum of 9.0. Maximal activity was obtained with a ratio of ATP/Mg2+ of 1 at 4–6mM. Above their optimal concentrations, ATP and Mg2+, separately or in combination, were inhibitory. Dithiothreitol at 3 mM stimulated the reaction by about 30%. The Km for adrenaline, determined by the sulphotransferase reaction and by the three-step (sulphate-activating and sulphotransferase) reactions was 125 micrometer. The rate of synthesis of [14C]-adrenaline sulphate, expressed in pmol/min per mg of protein for the livers of dog, monkey, rat, guinea pig and rabbit were, respectively, 144, 77, 47, 11 and 6. The corresponding values for the small intestines of dog and monkey were 60 and 62. Brain and heart tissues showed no measurable activity.