ACID CATALYSIS IN THE FORMATION OF DIOXOPIPERAZINES FROM PEPTIDES CONTAINING TETRAHYDROISOQUINOLINE-3-CARBOXYLIC ACID AT POSITION-2

Citation
S. Capasso et al., ACID CATALYSIS IN THE FORMATION OF DIOXOPIPERAZINES FROM PEPTIDES CONTAINING TETRAHYDROISOQUINOLINE-3-CARBOXYLIC ACID AT POSITION-2, International journal of peptide & protein research, 45(6), 1995, pp. 567-573
Citations number
24
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Biology
ISSN journal
0367-8377
Volume
45
Issue
6
Year of publication
1995
Pages
567 - 573
Database
ISI
SICI code
0367-8377(1995)45:6<567:ACITFO>2.0.ZU;2-1
Abstract
The kinetics of the spontaneous formation of 2,5-dioxopiperazines from peptides containing the Tic (1,2,3,4-tetrahydroisoquinoline-3-carboxy lic acid) residue in the 2-position of the sequence has been studied i n DMSO and water solution. The reaction is first order in Tic-peptide and subject to general-acid catalysis. Moreover, only the fraction of peptide having the amino terminal group in the deprotonated state reac ts with appreciable rate. In pure organic solvent, and in aqueous solu tion with low buffer concentration, the degradation reaction of Tic-pe ptides is very low; at 20 degrees C for the peptide H-Tyr-Tic-Phe-Phe- NH2, in DMSO and in neutral water in the absence of buffer, the half-l ives (t(1/2)) are 3 x 10(4) and 1.2 x 10(4) h, respectively. The addit ion of carboxylic acids or buffers to the reaction solutions markedly increases the reaction rate; in 0.01 M HAc in DMSO and in 0.1 M phosph ate buffer in water, pH 7.1, t(1/2) values for the tetrapeptide are 61 and 121 h, respectively. (C) Munksgaard 1995.