A factor-dependent sulfotransferase specific for 3?-phosphoadenosine-5?-phosphosulfate (PAPS) in the Cyanobacterium Synechococcus 6301

Abstract

A sulfotransferase isolated from the Cyanobacterium Synechococcus 6301 was found to be specific for 3′-phosphoadenosine-5′-phosphosulfate (PAPS). The molecular weight of this transferase has been estimated on a Sephadex-G-100 column to be about 58,000. The K _m for PAPS was determined to be 20 μM. The pH optimum was 8.0. The thiol dithioerythritol was needed for activity; other thiols such as glutathione, cysteine, or mercaptoethanol did not catalyze this reaction. The transferase, however, could not react directly with the thiol. A heat-stable factor was needed in this reaction. This factor was purified by conventional techniques and its molecular weight was determined on a Sephadex-G-50 column to be about 11,500. The factor showed normal Michaelis-Menten behavior toward the PAPS-sulfotransferase. It has been identified as thioredoxin. The tranferase was inhibited by 3′-5′-ADP and 2′–5′-ADP; all other adenine-containing nucleotides such as 2′-AMP, 3′-AMP, 5′-AMP, ADP, and c-AMP did not influence this reaction.