HGAPDH

Peptides have become an attractive drug discovery modality alongside small molecule compounds and high molecular weight biomolecules because they bind strongly to their target molecules. Previously, we found that secreted extracellular human GAPDH exhibits inhibitory activity against cancer cell growth. We sought to identify the minimal peptide sequence required for GAPDH activity in an effort to develop a small GAPDH-derived peptide with anti-cancer activity. Moreover, derivatives of the identified peptide, in which some amino acid residues were substituted with unnatural amino acids, were found to show stronger anti-cancer activity than non-substituted peptides.

The goal of the present work was expression of human glyceraldehyde-3-phosphate dehydrogenase (hGAPDH) without additional tag constructions in E. coli cells and elaboration of the procedure for purification of untagged hGAPDH from the extract of the producer cells. We present a simple method for purification of untagged hGAPDH including ammonium sulfate fractionation and gel filtration on a G-100 Sephadex column. The method allows isolation of 2 mg of pure hGAPDH from 600 ml of cell culture (7 g of the cell biomass). The specific activity of the freshly purified hGAPDH constitutes 117 ± 5 μmol NADH/min per mg protein (pH 9.0, 22 °C), which is close to the specific activity of rabbit muscle glyceraldehyde-3-phosphate dehydrogenase determined under the same conditions and several times exceeds the specific activity of his-tagged GAPDH preparations. The high enzymatic activity suggests that the recombinant enzyme retains its native structure. The described procedure may be useful for researchers who need a preparation of native hGAPDH without admixture of misfolded forms for their investigations.