Non-radioactive Adenosine 5′-Phosphosulfate Sulfotransferase Assay by Coupling with Sulfite Reductase and O-Acetylserine(thiol)lyase

Abstract

Adenosine 5′-phosphosulfate (APS) sulfotransferase is thought to be an enzyme that transfers the sulfo-group of APS to a carrier compound with a thiol group in the assimilatory sulfate reduction pathway of higher plants. We developed a rapid, non-radioactive assay for APS sulfotransferase. Sulfite released by APS sulfotransferase reaction in the presence of excess dithiothreitol was further converted to cysteine by coupling with yeast sulfite reductase and cabbage O-acetylserine(thiol)lyase. The cysteine thus formed was measured colorimetrically. By this method, 5 to 300 nmol of sulfite could be assessed. When the method was applied to APS sulfotransferase, the enzyme activity was APS-dependent with the partially purified enzyme. We could also detect APS sulfotransferase activity in some higher plants by this method.

Key words:

• adenosine 5′-phosphosulfate
• adenosine 5′-phosphosulfate sulfotransferase
• enzyme assay
• higher plants