BackgroundPalifermin (trade name Kepivance®) is an amino-terminally truncated recombinant human keratinocyte growth factor 1 (KGF-1) with 140 residues that has been produced usingEscherichia colito prevent and treat oral mucositis following radiation or chemotherapy. In this study, an amino-terminally shortened KGF-1 variant with 135 residues was produced and purified inE. coli, and its cell proliferation activity was evaluated.ResultsWe expressed soluble KGF-1 fused to thioredoxin (TRX) in the cytoplasmic fraction ofE. colito improve its production yield. However, three N-truncated forms (KGF-1 with 140, 138, and 135 residues) were observed after the removal of the TRX protein from the fusion form by cleavage of the human enterokinase light chain C112S (hEKLC112S). The shortest KGF-1 variant, with 135 residues, was expressed by fusion with TRX via the hEKLcleavage site inE. coliand purified at high purity (> 99%). Circular dichroism spectroscopy shows that purified KGF-1135had a structure similar to that of the KGF-1140as a random coiled form, and MCF-7 cell proliferation assays demonstrate its biological activity.ConclusionsWe identified variations in N-terminus-truncated KGF-1 and selected the most stable form. Furthermore, by a simple two-step purification, highly purified KGF-1135was obtained that showed biological activity. These results demonstrate that KGF-1135may be considered an alternative protein to KGF-1.Supplementary InformationThe online version contains supplementary material available at 10.1186/s12934-023-02097-z.