Studies on the PEGylation of Protein at a Specific Site: Sulfhydryl-PEGylation of 97Cys-IFN-gamma.

Human recombinant interferon-gamma(IFN-gamma) is not glycosylated at site 25 Asn or 97 Asn, but its bioactivity is the same as the native one. So we suppose that mutants 25/97Cys-IFN-gamma and PEG-25/97-Cys-IFN-gamma have the same bioactivity as native. By site-directed mutagenesis, the 97Cys-IFN-gamma was obtained and modified with a new PEGylation reagent which was prepared by us with a very simple method. The results were coincident with our previous supposition that mutagenesis at glycosylation site 97 from Asn to Cys and PEGylation at 97 Cys have no effect on the activity of IFN-gamma, which were about 7x10(6) IU/mg. If the work was of universal significance, it will be important both in theory and application. Therefore, further study will be done in the future.