Human platelet phenol sulfotransferase: partial purification and detection of two forms of the enzyme.
To begin to study the usefulness of platelet phenol sulfotransferase (PST) as a possible measure of the enzyme activity in other organs such as the brain, we purified human platelet PST 36-120-fold. Activity toward 3-methoxy-4-hydroxyphenylglycol (MHPG), dopamine, 5-hydroxytryptamine (5-HT), and phenol eluted in the same Sephadex G-100 and Affi-Gel Blue column fractions. Specific activities of the enzyme with MHPG, dopamine, 5-HT, and phenol as substrates were 1198, 1068, 401, and 408 units/mg protein, respectively. Optimal assay conditions were established for each substrate. Apparent Km values were 598 microM, 21 microM, 19 microM, and 500 microM for MHPG, dopamine, phenol, and 5-HT, respectively. Apparent Km values for 3'-phosphoadenosine-5'-phosphosulfate (PAPS) with the same four substrates ranged from 0.11 to 0.25 microM. The pH optima were 6.3 for phenol, 6.8 for dopamine, and 7.0 for MHPG and 5-HT. An additional pH optimum at 8.6 was present for 5-HT. A thermolabile form of the enzyme measured with dopamine and 5-HT, as well as a thermostable form measured with phenol, were present. Dichloronitrophenol (10(-5) M) noncompetitively inhibited the thermostable enzyme activity by 96% but decreased the thermolabile activity by only 36%. These studies provide the basis for a more accurate comparison of human platelet PST with the enzyme in the human brain and in other tissues.
D015239:Arylsulfotransferase; D001792:Blood Platelets / Q000201:enzymology*; D004298:Dopamine / Q000378:metabolism; D006801:Humans; D007527:Isoenzymes / Q000302:isolation & purification*; D008734:Methoxyhydroxyphenylglycol / Q000378:metabolism; D008970:Molecular Weight; D009596:Nitrophenols / Q000494:pharmacology; D019800:Phenol; D010636:Phenols / Q000378:metabolism; D010724:Phosphoadenosine Phosphosulfate / Q000378:metabolism; D012701:Serotonin / Q000378:metabolism; D013466:Sulfurtransferases / Q000302:isolation & purification*
D007527:Isoenzymes; D009596:Nitrophenols; D010636:Phenols; D012701:Serotonin; D019800:Phenol; D010724:Phosphoadenosine Phosphosulfate; D008734:Methoxyhydroxyphenylglycol; C015802:2,6-dichloro-4-nitrophenol; D013466:Sulfurtransferases; D015239:Arylsulfotransferase; D004298:Dopamine