The present invention provides a polypeptide comprising an amino acid sequence in which at least one amino acid is deleted, substituted or added in an amino acid sequence of isopropylmalate isomerase derived from a microorganism belonging to coryneform bacteria, wherein a coryneform bacterium which produces the polypeptide comprising the amino acid sequence as the sole isopropylmalate isomerase exhibits a partial leucine requirement in a minimal medium; a DNA encoding the polypeptide, a recombinant DNA comprising the DNA, a microorganism transformed with the recombinant DNA, and a process for producing an L-amino acid using the microorganism.