Further studies on the chemical cleavage of an N-terminal extra methionine from recombinant methionylated proteins

An additional methionine residue of recombinant human growth hormone (hGH) was converted into an oxoacyl form with glyoxylic acid, copper(II) sulfate and pyridine, and then cleaved from the rest of the protein with 3,4-diaminobenzoic acid in the presence of 1 M AcOH and 2 M HCO2Na. The conditions for N-terminal methionine cleavage worked better than the previous conditions with 1,2-phenylenediamine. The same protocol was also applicable to the methionylated forms of recombinant human betacellulin (BTC), neurotrophin-3 (NT-3) and human interleukin-2 (IL-2). The conversion yield for hGH, BTC, NT-3 and IL-2 increased up to approximately 80, 70, 55 and 50%, respectively. These results indicate that non-methionylated recombinant proteins could be prepared from the methionylated derivatives by chemical methods.