Characterization of Bovine Heart Sulfotransferase Catalyzing the Sulfation of Tyrosine-Containing Peptides

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Using [35S]PAPS as the sulfate donor, we have detected a sulfotransferase from bovine heart which catalyzes the sulfation of tyrosine-containing peptides. The enzyme displayed optimal activity at pH 5.75 and 35°C in a one-hour reaction. The addition of 10 mM Mn2+ or Co2+ to the reaction mixture increased the sulfotransferase activity by 3.4 and 3.5-fold, respectively. In contrast, the maximum increment stimulated by Mg2+ was only 1.75-fold at 15 mM concentration, and instead of exerting an enhancement effect, Ca2+ was found to be a potent inhibitor. The addition of 50 mM NaF to the reaction mixture resulted in an increase in sulfotransferase activity of 3.3-fold. The Km for 3'-phosphoadenosine 5'-phosphosulfate (PAPS) was determined to be 2μM at a constant 0.5 mM Boc-Glu-Asp-Tyr-Val. Among the 10 peptides tested as substrates, Boc-Glu-Asp-Tyr-Val and Boc-Asp-Asp-Tyr-Val provided the highest activities.
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