Manganese stimulation and stereospecificity of the Dopa (3,4-dihydroxyphenylalanine)/tyrosine-sulfating activity of human monoamine-form phenol sulfotransferase. Kinetic studies of the mechanism using wild-type and mutant enzymes.
Kinetic studies were performed to dissect the mechanism underlying the remarkable Mn(2+) stimulation of the Dopa/tyrosine-sulfating activity of the human monoamine (M)-form phenol sulfotransferase (PST). The activities and the stimulation by Mn(2+) are highly stereospecific for the d-form enantiomers of tyrosine and Dopa. Analysis of the kinetic results strongly suggests that tyrosine-Mn(2+) and tyrosine-Mn(2+)-tyrosine complexes are obligatory substrates, whereas Dopa-Mn(2+) complexes may be better substrates than Dopa alone. This activation of the Dopa/tyrosine-sulfating activity of M-form PST by Mn(2+) via complex formation between Mn(2+) and the substrate is the first reported case of a regulatory mechanism in this important class of enzymes. Our previous studies using point-mutated M-form PSTs established that the Mn(2+) (in the substrate-Mn(2+) complex) exerts its stimulatory effect by binding predominantly to the Asp-86 residue at the active site. We present here further studies using dopamine as substrate to bolster this conclusion. The possible physiological implications of this rather unusual specificity for the d-amino acid and its derivatives and the stimulation by Mn(2+) are discussed in the context of protective and detoxification mechanisms that may operate in neurodegenerative processes in the brain. The Mn(2+) stimulation of the activity of M-form PST toward d-enantiomers of Dopa/tyrosine may have implications for other substrates (including chiral drugs) and for the other cytosolic sulfotransferases that are involved in the regulation of endogenous metabolites as well as in detoxification.
Pai
T Govind
TG
Biomedical Research Center, The University of Texas Health Center, Tyler 75708, USA.
Ohkimoto
Kei
K
Sakakibara
Yoichi
Y
Suiko
Masahito
M
Sugahara
Takuya
T
Liu
Ming-Cheh
MC
D015239:Arylsulfotransferase / Q000378:metabolism; D001921:Brain / Q000378:metabolism; D002614:Chelating Agents / Q000494:pharmacology; D002855:Chromatography, Thin Layer; D018076:DNA, Complementary / Q000378:metabolism; D004295:Dihydroxyphenylalanine / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004492:Edetic Acid / Q000494:pharmacology; D006801:Humans; D007700:Kinetics; D008345:Manganese / Q000378:metabolism*; D017354:Point Mutation; D011994:Recombinant Proteins / Q000378:metabolism; D013237:Stereoisomerism; D015238:Sulfotransferases / Q000235:genetics* / Q000378:metabolism*; D013997:Time Factors; D014443:Tyrosine / Q000378:metabolism
D002614:Chelating Agents; D018076:DNA, Complementary; D011994:Recombinant Proteins; D014443:Tyrosine; D008345:Manganese; D004295:Dihydroxyphenylalanine; D004492:Edetic Acid; D015238:Sulfotransferases; D015239:Arylsulfotransferase; C403170:monoamine-sulfating phenol sulfotransferase