DEPENDENCE OF CATALYSIS AND CO2 O-2 SPECIFICITY OF RUBISCO ON THE CARBOXY-TERMINUS OF THE LARGE SUBUNIT AT DIFFERENT TEMPERATURES/

Variations in length and charge of the C-terminus of the Rubisco large subunit (L) can be seen in L from different phylogenetic lineages. We examined the catalytic parameters of Rubisco from higher plants and f rom engineered Synechococcus rbcL in relation to differences in the C- terminus. Among three selected higher plants, spinach, wheat, and Flav eria pringlei, spinach Rubisco with the shortest C-tail extension (D-4 73 + 2) showed the lowest temperature response. The response of Rubisc o from wheat (D-473 + 4) was intermediate, and the enzyme from F. prin glei (D-473 + 12) displayed the highest temperature response in terms of V-max for the carboxylase reaction. This observation was further in vestigated in a model system: the temperature-response for carboxylati on was enhanced after lengthening the C-terminus of the Synechococcus large subunit protein by two amino acid residues (DK). The results poi nt towards the length of the C-terminus as an additional factor for co ntrolling Rubisco activity, especially as an adaptation that widens th e temperature range in which the enzyme can function. Longer C-termini , we suggest, could establish additional interactions with the protein surface.