Abstract: The present invention relates to an altered-type human ALT gene in which the codons for the five amino acids in the human ALT (alanine aminotransferase) gene are replaced, i. e. the fourth amino acid codon from the initiation codon for methionine (Met) is replaced by a codon for serine (Ser), the fifth by a codon for threonine (Thr), the seventh by a codon for aspartic acid (Asp), the 39th by a codon for glycine (Gly) and the 222nd by a codon for alanine (Ala), and concurrently, restriction sites are added at the upstream and downstream of said gene. The active human ALT having properties similar to those of the native enzyme can be effectively produced by culturing E. coli transformed with a recombinant plasmid in which the altered-type human ALT gene of the present invention is ligated to a vector.

Abstract: The invention relates to a mutated human ALT (alanine aminotransferase) gene improving the DNA sequence encoding the N-terminal region of human ALT, without causing amino acid substitution, while, at the same time, adding restriction endonuclease sites to the upstream and downstream sites of the gene. By cultivation of E. coli transformant carrying a recombinant plasmid, which was constructed by ligation of the mutated human ALT gene into a vector, an active human ALT can be produced efficiently.