Deamidation at asparagine-88 in recombinant human interleukin 2

Reversed-phase high-performance liquid chromatography (RP-HPLC) and protein-chemical analysis revealed that only Asn88 in recombinant human interleukin 2 (rIL-2) is liable to be deamidated during a long period of storage in aqueous solutions (pH 5.0) at 25 degrees C, even though there are eight asparagine and six glutamine residues. The deamidation occurred more easily at 40 degrees C than at 25 degrees C but did not occur at all at temperatures below 5 degrees C. The biological activity of Asn88-deamidated rIL-2 was found to be almost the same as that of intact rIL-2, whereas its isoelectric point (pI 7.6) is different from that of intact rIL-2 (pI 7.9).