Transglutaminase‐mediated methods for site‐selective modification of human growth hormone

Two methods for the site-selective modification of native human growth hormone (hGH) using microbial transglutaminase were developed. In the first method, 1,3-bisaminoxypropane was attached to hGH, providing a direct incorporation of reactive aminoxy groups for further modification. The reaction was shown to be selective for Gln 141 , with minor modification at Gln 40 . In the second method, modified glutamine substrates were developed for attachment to Lys 145 in hGH. A series of glutamine-substrates were screened, and it was shown that microbial transglutaminase was selective towards substitutions on the glutamine core structure. Products from both methods could be transformed to site selectively mono-PEGylated hGH-derivatives in good isolated yield.