ATP Sulfurylase Activity in the Soybean [Glycine max (L.) Merr.].

ATP sulfurylase activity was assayed in soybean leaf extracts. A simple, rapid assay system using molybdate as an analogue of sulfate was developed. The assay was coupled to inorganic pyrophosphatase. The high pyrophosphatase level in soybean leaf extracts obviated the necessity of adding this enzyme to the assay system. ATP sulfurylase has a pH maximum above 7.5, uses molybdate and ATP as substrates, and requires magnesium ions for activity.