Selective removal of N-terminal methionine from recombinant human growth hormone by an aminopeptidase isolated from Aspergillus flavus

An aminopeptidase was isolated from a soil fungus, which specifically cleaves the unnatural N-terminal methionine in recombinant human growth hormone. Reaction mixtures with different ratios of aminopeptidase to recombinant methionyl human growth hormone showed that the removal of N-terminal methionine was complete at 1:200 (w/w), and more than 90% complete at ratios up to 1:2000 (w/w) when incubated for 24 h at 37°C. The data indicate that the aminopeptidase we have purified can be used for the efficient conversion of unnatural recombinant proteins to their natural form. Received 18 September 1997/ Accepted in revised form 17 April 1998