Human platelet phenolsulphotransferase: separate control of the two forms and activity range in depressive illness

Human phenolsulphotransferase exists in two forms, one specific for dopamine and tyramine, termed "M" and one for phenol, termed "P". In this study we have shown that these two forms are under separate control by correlating their activities in different individuals using different substrates. There was a highly significant correlation between the activities with dopamine, p-tyramine and 4-hydroxy-3-methoxyphenylglycol, but no significant correlation between the activities with any of these three substrates and that with phenol. Neither age nor sex had any effect on platelet phenolsulphotransferase "M" or "P" activities. Nor was there any significant correlation between platelet monoamine oxidase activity and phenolsulphotransferase "M" or "P" activities. Human platelet phenolsulphotransferase "M" was found to be unstable at temperatures above 35 degree C and it lost substantial activity when stored deep frozen in isotonic saline. However it was stable for up to four months when stored in isotonic sucrose or 10 mmol/l phosphate buffer (pH 7.4). Phenolsulphotransferase "M" amd "P" activities were measured in platelets from depressed patients of a diagnostic type characterized by low output of tyramine-O-sulphate after oral tyramine loading but their enzyme activities were not different from those in two control groups.