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Falcon confirms zebrafish SULT1 ST2 (sult1st2/Q7ZUS4) is a cytosolic, PAPS-dependent
SULT1-family sulfotransferase that catalyzes O-sulfation of diverse phenolic substrates,
and explicitly disambiguates it from the distinct SULT2 ST2 family member.
"sult1st2 encodes a **cytosolic, PAPS-dependent SULT1-family sulfotransferase** capable of sulfating diverse phenolic substrates, with particularly strong activity toward **estrone** and measurable activity/kinetics toward **thyroid hormones (T3/T4)** and **environmental phenolic xenobiotics** such as hydroxychlorobiphenyls."
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The enzyme transfers a sulfonyl group from the universal donor PAPS to small molecules
with hydroxyl/amino groups, typically increasing water solubility and promoting excretion.
"transfer of a sulfonyl group from the universal sulfate donor **PAPS (3′-phosphoadenosine-5′-phosphosulfate)** to small molecules containing hydroxyl or amino groups"
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Conserved 5'-phosphosulfate-binding and 3'-phosphate-binding motifs provide mechanistic
evidence that sult1st2 is a functional PAPS-dependent cytosolic SULT enzyme.
"These motifs provide mechanistic evidence that sult1st2 encodes a functional PAPS-dependent cytosolic SULT enzyme."
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In vitro recombinant SULT1 ST2 shows high specific activity toward estrone and measurable
activity toward thyroid hormones T3/T4, plus flavonoids, 2-naphthol, and hydroxychlorobiphenyls,
supporting roles in endocrine hormone metabolism and xenobiotic detoxification.
"these data support a central role for sult1st2 in **phenolic xenobiotic sulfation** and in modulating endocrine molecules including **estrogens and thyroid hormones**."
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SULT1 ST2 sulfates hydroxychlorobiphenyls with low-micromolar Km, and zebrafish liver cells
form and release sulfated conjugates of these xenobiotics, supporting a detoxification/elimination role.
"supporting a role in **detoxification/inactivation and elimination** of environmental phenolic pollutants."
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The best-supported localization is intracellular cytosol, consistent with cloning/biochemistry
describing the enzyme as a cytosolic SULT1, with soluble ~35 kDa recombinant expression.
"the current best-supported localization is **intracellular cytosol**, plausibly in metabolically active tissues such as liver."
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RT-PCR detected SULT1 ST2 mRNA in cultured zebrafish liver cells and whole zebrafish,
consistent with a hepatic/organismal metabolic role.
"RT-PCR detected **SULT1 ST2 mRNA** in both **cultured zebrafish liver cells** and **whole zebrafish** samples."
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The only in vivo perturbation phenotype in the corpus is a morpholino knockdown of SULT2 ST2,
a different family member whose phenotype must not be transferred to sult1st2.
"A morpholino knockdown phenotype was found for **SULT2 ST2**, but this is a **different gene family member** and cannot be transferred to sult1st2."