FIELD: biotechnology, genetic engineering, enzymes, biochemistry. SUBSTANCE: mutant alpha-isopropylmalate synthase (IPMS) is obtained by deletion, substitution, insertion or addition of one or some amino acid residues. Properties of mutant IPMS are identical with natural DNA encoding IPMS of wild type and comprises mutation that allows to loss sensitivity to inhibitory effect by L-leucine by feedback inhibition mechanism. DNA transforms Escherichia coli strain that is cultured for L-leucine preparing. Invention ensures to increase the yield of L-leucine that is used as food supplement, reagent and growth factor. EFFECT: improved method of strain and L-leucine preparing. 6 cl, 3 tbl
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