A process for preparing a C7-C11 2-ketoacid comprising contacting a substrate, selected from 2-ketobutyrate and 2-ketoisovalerate, and a native or genetically modified LeuA enzyme having isopropylmalate synthase activity; a genetically modified LeuB' enzyme, wherein: (a) the enzyme is obtained from Escherichia coli and has an amino acid sequence corresponding to Sequence Listing, SEQ ID 1; the enzyme having been modified at Leu-96 by substituting glycine; at Val-198 by substituting alanine; at Leu-96 by substituting alanine and at Val-198 by substituting alanine; at Leu-96 by substituting glycine and at Val-198 by substituting alanine; at Leu-96 by substituting glycine and at Val-198 by substituting glycine; or at Leu-96 by substituting alanine; or (b) the enzyme has isopropylmalate dehydrogenase activity and catalyzes the conversion of 3-hexylmalate to form 2-ketononanoate at a catalytic efficiency that is higher than that of a native LeuB enzyme, wherein the enzyme has an amino acid sequence that is at least 60 percent homologous to the amino acid sequence of Sequence Listing, SEQ ID 1; the enzyme having been modified as in (a); and a native or genetically modified LeuCD' enzyme complex having isopropylmalate isomerase activity; under conditions such that the 2-ketobutyrate or 2-ketoisovalerate is converted, via one or more steps, to a C7-C11 2-ketoacid. a substrate, selected from 2-ketobutyrate and 2-ketoisovalerate, and a native or genetically modified LeuA enzyme having isopropylmalate synthase activity; a genetically modified LeuB' enzyme, wherein: (a) the enzyme is obtained from Escherichia coli and has an amino acid sequence corresponding to Sequence Listing, SEQ ID 1; the enzyme having been modified at Leu-96 by substituting glycine; at Val-198 by substituting alanine; at Leu-96 by substituting alanine and at Val-198 by substituting alanine; at Leu-96 by substituting glycine and at Val-198 by substituting alanine; at Leu-96 by substituting glycine and at Val-198 by substituting glycine; or at Leu-96 by substituting alanine; or (b) the enzyme has isopropylmalate dehydrogenase activity and catalyzes the conversion of 3-hexylmalate to form 2-ketononanoate at a catalytic efficiency that is higher than that of a native LeuB enzyme, wherein the enzyme has an amino acid sequence that is at least 60 percent homologous to the amino acid sequence of Sequence Listing, SEQ ID 1; the enzyme having been modified as in (a); and a native or genetically modified LeuCD' enzyme complex having isopropylmalate isomerase activity; a native or genetically modified LeuA enzyme having isopropylmalate synthase activity; a genetically modified LeuB' enzyme, wherein: (a) the enzyme is obtained from Escherichia coli and has an amino acid sequence corresponding to Sequence Listing, SEQ ID 1; the enzyme having been modified at Leu-96 by substituting glycine; at Val-198 by substituting alanine; at Leu-96 by substituting alanine and at Val-198 by substituting alanine; at Leu-96 by substituting glycine and at Val-198 by substituting alanine; at Leu-96 by substituting glycine and at Val-198 by substituting glycine; or at Leu-96 by substituting alanine; or (b) the enzyme has isopropylmalate dehydrogenase activity and catalyzes the conversion of 3-hexylmalate to form 2-ketononanoate at a catalytic efficiency that is higher than that of a native LeuB enzyme, wherein the enzyme has an amino acid sequence that is at least 60 percent homologous to the amino acid sequence of Sequence Listing, SEQ ID 1; the enzyme having been modified as in (a); and (a) the enzyme is obtained from Escherichia coli and has an amino acid sequence corresponding to Sequence Listing, SEQ ID 1; the enzyme having been modified at Leu-96 by substituting glycine; at Val-198 by substituting alanine; at Leu-96 by substituting alanine and at Val-198 by substituting alanine; at Leu-96 by substituting glycine and at Val-198 by substituting alanine; at Leu-96 by substituting glycine and at Val-198 by substituting glycine; or at Leu-96 by substituting alanine; or at Leu-96 by substituting glycine; at Val-198 by substituting alanine; at Leu-96 by substituting alanine and at Val-198 by substituting alanine; at Leu-96 by substituting glycine and at Val-198 by substituting alanine; at Leu-96 by substituting glycine and at Val-198 by substituting glycine; or at Leu-96 by substituting alanine; (b) the enzyme has isopropylmalate dehydrogenase activity and catalyzes the conversion of 3-hexylmalate to form 2-ketononanoate at a catalytic efficiency that is higher than that of a native LeuB enzyme, wherein the enzyme has an amino acid sequence that is at least 60 percent homologous to the amino acid sequence of Sequence Listing, SEQ ID 1; the enzyme having been modified as in (a); and a native or genetically modified LeuCD' enzyme complex having isopropylmalate isomerase activity; under conditions such that the 2-ketobutyrate or 2-ketoisovalerate is converted, via one or more steps, to a C7-C11 2-ketoacid.