Changes in ATP sulfurylase and adenosine 5′‐phosphosulfate sulfotransferase activity during autumnal senescence of beech leaves

Abstract

The decrease in extractable activity of ribuloscbisphosphate carboxylase (EC 4.1.1.39), ATP sulfurylase (EC 2.7.7.4) and adenosine 5′‐phosphosulfate sulfotransferase and the content in chlorophyll and protein was compared in leaves of cloned beech trees (Fagus sylvatica L.) during autumnal senescence. Leaves excised at the same time but containing different amounts of chlorophyll gave extracts with correspondingly varying amounts of ribulosebisphosphate carboxylase activity. Leaves which had almost completely lost this enzyme activity contained still appreciable ATP sulfurylase and adenosine 5′‐phosphosulfate sulfotransferase activity and soluble protein. For all components determined, there was a period lasting until mid or end of October during which there was no or only a small decrease. They were then all lost rapidly from the leaves. The specific activity of ribulosebisphosphate carboxylase decreased during this phase of rapid loss, whereas it remained essentially constant for ATP sulfurylase and adenosine 5′‐phosphosulfate sulfotransferase. During this period, the mean half life of ribulosebisphosphate carboxylase was shorter than the one of ATP sulfurylase and of adenosine 5′‐phosphosulfate sulfotransferase. These experiments clearly show that ribulosebisphosphate carboxylase was preferentially lost from beech leaves during autumnal senescence as compared to ATP sulfurylase and adenosine 5′‐phosphosulfate sulfotransferase.