Theoretical analysis of the kinetic isotope effect on carboxylation in RubisCO

Ribulose-1,5-bisphosphate carboxylase/oxygenase (RubisCO) fixes atmospheric carbon dioxide into bioavailable sugar molecules. It is also well known that a kinetic isotope effect (KIE; CO₂ carbon atoms) accompanies the carboxylation process. To describe the reaction and the KIE α, two different types of molecular dynamics (MD) simulations (ab initio MD and classical MD) have been performed with an Own N-layered Integrated molecular Orbitals and molecular Mechanics (ONIOM)-hybrid model. A channel structure for CO₂ transport has been observed during the MD simulation in RubisCO, and assuming the reaction path from the inlet to the product through the coordinate complex with Mg²⁺, simulations have been performed on several molecular configuration models fixing several distances between CO₂ and ribulose-1,5-bisphosphate along the channel. Free energy analysis and diffusion coefficient analysis have been evaluated for different phases of the process. It is confirmed that the isotopic fractionation effect for CO₂ containing either ¹³C or ¹²C would appear through the transiting path in the channel structure identified in RubisCO. The estimated isotope fractionation constant was quite close to the experimental value.     

Total Synthesis and Expressions in E. coli of Three Redesigned Genes for the Mature Small Subunit (rbcS) of Rubisco Fron Tobacco, Wheat and Rice

Three structural genes, which code for the mature small subunits (rbcS) of ribulose-1,5-bisphosphate carboxylase/oxygenase from tobacco, wheat and rice, respectively,have been redesignedwith the aid of a computer,totally synthesized by combining chemical method and enzymatic ligation,and expressed in E. coli with high yields.