Guanidination of Ovine Luteinizing Hormone and Effects on Activity

Abstract

The free amino groups in oLH, oLHα and oLHβ were guanidinated by O-methylisourea. The ϵ-NH₂ groups of lysine residues reacted to substitute these positions in the sequence with the more basic homoarginine residue. The α-NH₂ groups did not react under the conditions used. Guanidinated oLH or the products of guanidinated oLHα + native oLHβ or guanidinated oLHα + guanidinated oLHβ were inactive in two bioassay systems. Native oLHα + guanidinated oLHβ, however, showed potencies of 39% to 55% of that observed with the native subunit recombinant or native oLH. Possible structural implications for hormone-receptor site interactions are discussed.