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Human Platelet Phenol Sulfotransferase: Partial Purification and Detection of Two Forms of the Enzyme
Author(s) -
Butler Paula R.,
Anderson Robert J.,
Venton Duane L.
Publication year - 1983
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1983.tb04788.x
Subject(s) - thermolabile , sephadex , chemistry , dopamine , phenol , enzyme , chromatography , sulfotransferase , specific activity , enzyme assay , substrate (aquarium) , platelet , biochemistry , elution , cofactor , endocrinology , medicine , organic chemistry , biology , ecology
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 K m values were 598 μ M , 21 μ M , 19 μ M , and 500 μ M for MHPG, dopamine, phenol, and 5‐HT, respectively. Apparent K m values for 3′‐phosphoadenosine‐5′‐phosphosulfate (PAPS) with the same four substrates ranged from 0.11 to 0.25 μ M . 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.