Solubilization of histamine H-1, GABA and benzodiazepine receptors.

Dopamine 3-0-sulfate is present in considerable amounts in mammalian plasma and peripheral tissues. Incubation of dopamine 3-0-sulfate (0.1 μmole) with purified bovine dopamine-β-hydroxylase resulted in the formation of free norepinephrine (7.3 × 10^?3 μmole). The conversion to norepinephrine was inhibited by 0.6 mM of fusaric acid, an inhibitor of dopamine-β-hydroxylase. The reaction of dopamine 3-0-sulfate with dopamine-β-hydroxylase followed Michaelis-Menten kinetics. The calculated K_m was 17 mM, different from the K_m for free dopamine (0.1 mM). The incubation medium does not contain any sulfatase activity.