Abstract
Sucrose phosphate synthase (SPS) is an important enzyme in the two-step biosynthesis of sucrose in photosynthetic organisms. SPS catalyzes the formation of Sucrose-6-phosphate which is subsequently converted to sucrose. SPS is believed to have regulatory roles in sucrose biosynthesis through interaction with Serine Kinase, 14-3-3 protein and SPP. Nevertheless, the protein-protein interaction sites on SPS are not well characterized. This study focuses on identification of functionally important residues other than the catalytic residues in SPS through evolutionary trace analysis and structural mapping of key residues. We found that other than catalytic sites, many residues are absolutely conserved and are either buried or exposed. The exposed highly conserved sites are putative protein-protein interaction sites. We have also identified residues which are class specifically conserved in SPS4. Mapping of the class specific residues on SPS crystal structure revealed their distribution close to the catalytic site. Therefore, the class specific conserved sites in SPS4 can be predicted to be influencing catalysis.