Concerning tryptic cleavages involving proline he wrote: "Proline residue
in position P'1 usually blocks trypsin action; however, the bond R-P can
be cleaved if preceded by Gln, as was observed for sequences -QR/PD,
-QR/PG, and -AGGR/PQ." (He gives 5 references) "A statistical study, made
with the help of the database LYSIS, has shown negative influences of
residues surrounding the R- and K-bonds during trypsin cleavages of a pool
of protein substrates. It illustrates in particular: the strong negative
influence of proline in position P'1 (which) is more pronounced for Lys-
than Arg-bonds, which is consistent with the role of Arg- as a stronger
substrate for trypsin than Lys-."
-Lowell Ericsson, Dept. of Biochemistry, U. of Washington, Seattle, WA
On Thu, 19 Nov 1998, Peter Hunziker wrote:
> long time ago my supervisors teached me that trypsin does never cleave the
> peptide-bond between LYS/ARG and PRO. Now, I also tell my students that
> this bond is not cleaved at all. However, in a recent LC/MS analysis we
> measured the masses of two peptides that indicated a tryptictic cleavage
> exactly at this bond (Enzyme: mod. trypsin from Promega). Since I could not
> believe it we additionally sequenced the peptides by Edman degradation and
> it turned out that trypsin has cleaved the LYS-PRO bond.
> On the C-terminal side of the cleavage site there were a number of GLY
> residues. Does anybody know if this may influences the specificity of the
> enzyme? Were my supervisors wrong and trypsin does cleave LYS/ARG-PRO bonds?
>
> best regards
> Petre
>
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