Activity and carboxylation specificity factor of mutant ribulose 1,5-bisphosphate carboxylase/oxygenase from...

The values of molecular carboxylase activity kcat and carboxylation specificity factor tau for mutant ribulose 1,5-bisphosphate carboxylase (rubisco) from Anacystis nidulans decreased as compared to those of the wild type recombinant rubisco. The substitution of five amino acid residues in rubisco large subunit Lys,Ala,Ser,Thr,Leu(339-343)Phe,Leu,Met,Ile,Lys had kcat decreased by 90% and tau by 36.3%. The same parameters for mutants with the single replacements decreased: for Thr342Ile kcat by 40.5% and tau by 16.7%, and for mutant Leu343Lys kcat by 48.1% and tau by 18.5%. Mutant rubisco with three amino acid residues changed Val,Asp,Leu(346-348)Tyr,His,Thr was inactive. The substitution Leu326Ile decreased kcat by 54.4% and tau by 34.2%; and change Ser328Ala decreased kcat only by 5.6% but tau by 41.5%. Replacement Asn123His decreased kcat by 16.5%. Significance of the non conservative amino acid residues for carboxylase activity and ribulose-1,5-bisphosphate partition is discussed.