HUMAN SKIN AND PLATELET MINOXIDIL SULFOTRANSFERASE ACTIVITIES - BIOCHEMICAL-PROPERTIES, CORRELATIONS AND CONTRIBUTION OF THERMOLABILE PHENOL SULFOTRANSFERASE

Human scalp skin high speed supernatants were used to test whether min oxidil sulfotransferase (MNX-ST) and phenol sulfotransferase (PST) act ivities were present. Platelet homogenates from the same skin donors w ere used to test whether levels of sulfotransferase activities in the blood platelet would reflect levels of the enzyme activities in skin. Dopamine, p-nitrophenol and minoxidil were used as substrates for skin and platelet thermolabile (TL PST), thermostable (TS PST) and MNX-ST activities, respectively. Biochemical properties of each skin enzyme w ere the same as the platelet enzymes with respect to apparent K-m valu es for substrates, pH optima, thermal stabilities and responses to inh ibition by 2,6-dichloro-4-nitrophenol (DCNP). An unexpected finding wa s that skin and platelet MNX-ST thermal stabilities and responses to D CNP were more similar to TL PST than to TS PST, the enzyme reported to be responsible for MNX-ST activity. There were significant positive c orrelations of platelet sulfotransferases with the relative levels of activities of the same skin sulfotransferases. Unexpected findings wer e significant positive correlations of MNX-ST and TL PST activities. P artially purified platelet TS PST assayed with minoxidil as the substr ate showed a response to DCNP and thermal stability that were the same as TS PST. Platelet TL PST assayed with minoxidil showed thermal stab ility and a response to DCNP that were essentially the same as TL PST. The results indicated that not only TS PST, but also TL PST activitie s in human skin and platelet contributed to MNX-ST activity. It will b e feasible to test whether measures of platelet PST activities will pr edict physiologic responses to minoxidil.