Pyroglutamyl residues

Synthesis of Peptides with endo-Pyroglutamyl Residues... 

Scheme 2 Synthesis of Peptides with Internal Pyroglutamyl Residues 351...

The substrate, Gln-Leu-Tyr-Glu-Asn-Lys-t-(dansyl)-OH, is separated from the product containing the N-terminal pyroglutamyl residue by chromatography on a Hypersil ODS column (4.6 mm x 100 mm). The mobile phase contained 100 mM sodium acetate (pH 6.5) in 24% acetonitrile. A fluorescence detector was used with excitation at 352 to 360 nm and emission at 482 nm. Fluorescence detection is about 100 times more sensitive than monitoring absorbance at 340 nm. 

MH - SO3) consistent with a single sulfate group and a pyroglutamyl residue in the structure. Basic hydrolysis of the... 

QRFP, a 43-peptide amide bearing an N-terminal pyroglutamyl residue and the C-terminal RFamide consensus motif. This novel RFamide peptide is implicated in food intake and aldosterone release from the adrenal cortex in the rat. QRFP is conserved in humans, cattle, rat, and mouse. The term QRFP is derived from pyroglutamylated arginine-phenylalanine-amide peptide [S. Fukusami et al., J. Biol. Chem. 2003, 278, 46387 C. Kutzleb et al., Curr. Prot. Pept. Sci. 2005, 6, 265]. 

Next to trypsin chymotrypsin is the most preferred proteolytic enzyme in sequencing. Its specificity is less absolute than that of trypsin. Primarily the bonds that follow phenylalanine, tyrosine and tryptophan are cleaved, but measurable hydrolysis takes place next to leucine and methionine residues as well. It is advisable, therefore, to determine in preliminary experiments the conditions (enzyme-substrate ratio, time, temperature) best suited for the formation of a few and well separable fragments. Occasionally also less specific enzymes, such as pepsin, papain or thermolysin find application in structure elucidation. For the hydrolysis of specific bonds new microbial proteases can be isolated. There are known prolidases and also enzymes which hydrolyze solely the bond which follows a pyroglutamyl residue and so on. 

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