Localization of adenosine 5'-phosphosulfate sulfotransferase in spinach leaves

Roots of spinach (Spinacia oleracea L.) seedlings contained only a very low activity of adenosine 5'-phosphosulfate sulfotransferase compared to the cotyledons. Adenosine 5'-phosphosulfate sulfotransferase activity increased about tenfold in cotyledons during greening. Preparation of organelle fractions from spinach leaves by a combination of differential and isopycnic density gradient centrifugation showed that adenosine 5'-phosphosulfate sulfotransferase banded with NADP-glyceraldehyde-3-phosphate dehydrogenase, a marker enzyme for intact chloroplasts. In the fractions of peroxisomes, mitochondria and broken chloroplasts virtually no adenosine 5'-phosphosulfate sulfotransferase activity was measured. Comparison with the chloroplast enzyme NADP-glyceraldehyde-3-phosphate dehydrogenase indicates that in spinach, adenosine 5'-phosphosulfate sulfotransferase is localized almost exclusively in the chloroplasts.