Human pheochromocytoma phenol sulfotransferase: biochemical properties and activities of thermolabile and thermostable forms.

To determine whether pheochromocytoma phenol sulfotransferase (PST) activities were similar to blood platelet PST activities, we established assay conditions and biochemical properties for the human pheochromocytoma enzymes. At least two forms of PST were present in high speed supernatant (HSS) preparations of the tumors. A thermolabile form (TL) and a thermostable form (TS) were similar to those of human platelet PST with regard to pH optima, apparent Km values, responses to 2,6-dichloro-4-nitrophenol and thermal stability. PST activities were measured in 74 tumors of neuroectodermal origin that had been stored at -80 degrees C for a mean of 37.9 months. Levels of TL and TS PST activities decreased in a nonlinear fashion with time of sample storage. TL and TS PST activities of 4 samples assayed after 1.08 +/- 1.95 (mean +/- SD) month of storage were 167 +/- 73 and 3,110 +/- 1,817 U/mg protein, respectively (mean +/- SEM). Our results indicated that the TL and TS forms of PST in pheochromocytoma HSS preparations were biochemically similar to platelet PST activities.