[Conformational aspects of peptide interaction with proteolytic enzymes. Pepsin-catalyzed hydrolysis of cyclic peptides, containing leucyl-tyrosine fragments].

Pepsin was found capable of splitting cycloota- and cyclodecapeptides cyclo (-L-leucyl-L-tyrosyl-glycln-), n=6 or 8. The 18-membered peptides cyclo(-L-leucyl-L-tyrosyl-glycyl4-) and cyclo(-L-leucyl-L-tyrosy-delta-aminovaleroyl2-) were found stable to the effect of pepsin. To study the kinectics of hydrolysis for tyrosine-containing substrates of pepsin, a method of isolation of the unsplit substrate using ion-exchange resins and quantitative spectrophotometric estimation by absortion of tyysis of cycoocta and cyclodecapeptides was characterized by Km and kcat values.