title: On the role of tryptophan in luteinizing-hormone-releasing hormone (luliberin).
abstract: The tryptophan residue of luteinizing-hormone-releasing hormone (luliberin) was chemically modified to produce the following analogs: [Trp(o)3]luliberin, Trp-(2,4-dinitrophenylsulfenyl)-luliberin, Trp-(2-hydroxy-5-nitrobenzyl)luliberin, (Trp-S-luliberin)2, Trp-CH3S-luliberin and Trp-formyl-luliberin. The luteinizing-hormone-releasing activity of those analogs was determined by bioassay in vitro and found to be 0.2%, 0.2%, 0.6%, 1.5%, 1.7% and 7% of that of the natural hormone, respectively. These results demonstrate that alterations in the indole moiety of tryptophan-3, which lead to a reduction in its electron density or sterically restrict its electron avaliability, are associated with a dramatic loss of biological activity.
mesh_terms: D000818:Animals; D001681:Biological Assay; D005260:Female; D007987:Gonadotropin-Releasing Hormone / Q000031:analogs & derivatives* / Q000494:pharmacology; D010902:Pituitary Gland / Q000187:drug effects / Q000502:physiology; D051381:Rats; D013056:Spectrophotometry, Ultraviolet; D013329:Structure-Activity Relationship; D014364:Tryptophan
chemical_list: D007987:Gonadotropin-Releasing Hormone; D014364:Tryptophan