NEW FLUOROGENIC SUBSTRATES FOR THE STUDY OF SECONDARY SPECIFICITY OF PROLYL OLIGOPEPTIDASE

The secondary specificity of prolyl oligopeptidase (POP) has been stud ied by using a series of fluorogenic substrates containing the highly fluorescent 7-amino-4-methyl-2-quinolinone (AMeq) marker. The substrat es were dipeptides of the general formula Z-X-Pro-NH-Meq, bearing amin o acid residues with variable functional groups [Met, Lys(Boc), Lys, H is, Ser, Leu, Glu(OMe), Glu, Cys(Bzl)] at the P-2 position, and the tr ipeptide Z-Asn-Cys(Bzl)-Pro-NH-Meq. The kinetic parameters for their h ydrolysis by porcine kidney POP were determined at lambda(ex) = 360 nm and lambda(em) = 430 nm. All the dipeptide substrates showed a high a ffinity to the enzyme and could be used for its fluorometric determina tion. The S-2 binding subsite of POP can accomodate amino acid residue s with a bulky side group, while it prefers a positively charged group (free Lys) instead of a negatively charged one (free Glu). (C) Munksg aard 1997.