Several agonists of luteinizing hormone-releasing hormone (LHRH) are currently used for different therapeutic purposes, but relatively little is known about their metabolic fate after administration. This paper describes the application of high-performance liquid chromatography combined with off-line fast atom bombardment mass spectrometry to identify the degradation products resulting from the incubation of LHRH analogues with proteolytic enzymes. Three analogues, containing a ψ(E,CH=CH) pseudo-peptide bond were synthesized and afforded to the assay to determine the resistance against α-chymotrypsin and subtilisin: [Tyr5 ψ(E,CH=CH)Gly6]LHRH, [Gly6 ψ(E,CH=CH)D,L-Leu7]LHRH and [Pro9 ψ(E,CH=CH)Gly10]LHRH. The pattern of peptide metabolites identified by this method indicates that α-chymotrypsin degrades LHRH analogues at the Trp3-Ser4 and Tyr5-Gly6 bond, while subtilisin hydrolyzes only the Tyr5-Gly6 linkage. The results also indicate a possible stabilization of native amide bonds against enzymatic degradation by neighbouring ψ(E,CH=CH) modifications.
- Liquid chromatography-mass spectrometry
- Luteinizing hormone-releasing hormone
ASJC Scopus subject areas
- Analytical Chemistry
- Organic Chemistry