A method of generating a Rubisco protein with an improved functional property selected from the group consisting of improved kinetic efficiency of the Rubisco, an increased specificity for carbon dioxide over oxygen of the Rubisco, an altered specificity of the Rubisco for one or more substrates, an altered specificity for one or more products of the Rubisco and an altered effective temperature range for Rubisco catalysis, the method comprising: (a) identifying at least one Target amino acid Residue in a first Rubisco protein, wherein said Target amino acid Residue is associated with said functional property, wherein the Target amino acid Residues of the Rubisco protein are first shell residues which directly coordinate with the reaction centre or second shell residues which directly coordinate with one or more of the first shell residues, wherein said first shell residues of Rubisco are selected from the group consisting of GLU60, ASN123, LYS175, LYS177, KCX201, ASP203, GLU204 and HIS294, wherein residue numbering is from spinach Rubisco, and KCX201 denotes carbamylated LYS201; (b) comparing at least one homologous second Rubisco protein from the same or a different phylogenetic branch as the first Rubisco protein with the first Rubisco protein and identifying at least one Variant amino acid Residue between the first Rubisco protein and the second Rubisco protein, wherein the residues of the second Rubisco protein used for comparison with the first Rubisco protein comprise all residues directly co-ordinated to the active site of a Rubisco protein, all residues interacting with the reactive centre of the substrate or intermediate reaction species of a Rubisco protein, and other residues within a proximate distance of between 3 and 28 Ǻ from any atom of substrate or intermediate reaction species from the active site of a Rubisco protein or a subset of such residues; (c) selecting at least one Candidate amino acid Residue from the Variant amino acid Residues identified in (b) based on assessing the spatial proximity of the Variant Residues to the Target Residues and estimating and ranking their ability to influence the electrostatics and orientation of the Target Residues and modulate the functional property of the formed protein; (d) producing at least one Candidate Mutant Rubisco protein in vitro in which said at least one Candidate amino acid Residue from the second Rubisco protein substitutes a corresponding residue in the first Rubisco protein; and (e) screening said at least one Candidate Mutant Rubisco protein produced in (d) to identify a Rubisco protein having said improved functional property. (a) identifying at least one Target amino acid Residue in a first Rubisco protein, wherein said Target amino acid Residue is associated with said functional property, wherein the Target amino acid Residues of the Rubisco protein are first shell residues which directly coordinate with the reaction centre or second shell residues which directly coordinate with one or more of the first shell residues, wherein said first shell residues of Rubisco are selected from the group consisting of GLU60, ASN123, LYS175, LYS177, KCX201, ASP203, GLU204 and HIS294, wherein residue numbering is from spinach Rubisco, and KCX201 denotes carbamylated LYS201; (b) comparing at least one homologous second Rubisco protein from the same or a different phylogenetic branch as the first Rubisco protein with the first Rubisco protein and identifying at least one Variant amino acid Residue between the first Rubisco protein and the second Rubisco protein, wherein the residues of the second Rubisco protein used for comparison with the first Rubisco protein comprise all residues directly co-ordinated to the active site of a Rubisco protein, all residues interacting with the reactive centre of the substrate or intermediate reaction species of a Rubisco protein, and other residues within a proximate distance of between 3 and 28 Ǻ from any atom of substrate or intermediate reaction species from the active site of a Rubisco protein or a subset of such residues; (c) selecting at least one Candidate amino acid Residue from the Variant amino acid Residues identified in (b) based on assessing the spatial proximity of the Variant Residues to the Target Residues and estimating and ranking their ability to influence the electrostatics and orientation of the Target Residues and modulate the functional property of the formed protein; (d) producing at least one Candidate Mutant Rubisco protein in vitro in which said at least one Candidate amino acid Residue from the second Rubisco protein substitutes a corresponding residue in the first Rubisco protein; and (e) screening said at least one Candidate Mutant Rubisco protein produced in (d) to identify a Rubisco protein having said improved functional property.