Regulation of self‐glycosylation of reversibly glycosylated polypeptides from Solanum tuberosum

Reversibly glycosylated polypeptides (RGPs) belong to a family of self‐glycosylating proteins believed to be involved in plant polysaccharide synthesis. The precise function of these enzymes remains to be elucidated. Our results showed that the RGP 38‐kDa subunit is phosphorylated in potato extracts ( Solanum tuberosum L.). An increase in the self‐glycosylation of Solanum tuberosum RGP (StRGP) 38‐kDa subunit was observed after alkaline phosphatase (AP) treatment. Our results suggest that phosphorylation of StRGP appears to regulate its self‐glycosylation. It was determined that when the StRGP reaction was carried out in the presence of UDP‐[ 14 C]Glc as the sugar donor and then 1 m M UDP was added in a chase‐out experiment, radioactive UDP‐Glc was obtained indicating that StRGP reaction seems to be reversible. The anomeric configuration of transferred sugars to StRGP protein was also studied.