A method for the production of the α-chain of hepatocyte growth factor or an N-terminal fragment thereof (NK polypeptide) by expression of a nucleic acid encoding said NK polypeptide in a microbial host cell, isolating inclusion bodies containing said NK polypeptide in denatured form, solubilization of the inclusion bodies and naturation of the denatured NK polypeptide, which is characterized in that in said nucleic acid at least one of the codons of amino acids selected from the group consisting of codons at positions 33, 35 and 36 is CGT, results in an improved expression yield.