Z-GLY-PRO-AMC

Background: Fibroblast activiation protein alpha (FAP) is considered a diagnostic and prognostic biomarker for various types of cancer. FAP shares substrate specificity with prolyl oligopeptidase (PREP), studied in (neuro)inflammation and neurodegeneration as well as cancer. Current assays inadequately discriminate between FAP and PREP and there is need for an assay that reliably quantitates the FAP/PREP activity ratio in plasma. Methods: FAP and PREP activities were measured in human EDTA-plasma in presence of well characterized PREP and FAP inhibitors. Results: A combined kinetic assay was developed in conditions to optimally measure FAP as well as PREP activity with Z-Gly-Pro-AMC as substrate. Limit of detection was 0.009 U/L and limit of quantitation was 0.027 U/L for the combined FAP-PREP assay. Within-run coefficient of variation was 3% and 4% and between-run precision was 7% and 12% for PREP and FAP, respectively. Accuracy was demonstrated by comparison with established end-point assays. Hemolysis interferes with the assay with 1.5 g/L hemoglobin as cut-off value. PREP (but not FAP) activity can increase upon lysis of platelets and red blood cells during sample preparation. Conclusion: With this new assay, on average 67% of the Z-Gly-Pro-AMC converting activity in plasma can be attributed to FAP.

Two isoforms, Bmpop-a and Bmpop-b, were cloned and characterized, which were found to encode prolyl oligopeptidase (Pop) of the domestic silkworm Bombyx mori. The full lengths of Bmpop-a and Bmpop-b were 2497 and 2508 bp, deducing 707 and 740 amino acids, respectively. Both of them, possessing the typical characteristics of the Pop family of serine proteinase, were detected to be expressed among different tissues and development stages at the transcription and translation levels. Soluble recombinant BmPop-a (rBmPop-a) had oligopeptidase activity toward the substrates, Z-Gly-Pro-pNA, Z-Gly-Pro-AMC and angiotensin I. An inhibition assay showed that the activity of rBmPop-a was significantly inhibited by KYP-2047 and S17092 in vitro. BmPop-b was identified in the molting fluids at three different stages by Western blotting analysis, showing a predominant expression in the integument. Two isoforms of Bmpop gene and other three genes in the renin-angiotensin system (RAS) in the integument were down-regulated by starvation treatments but up-regulated by refeeding. These results suggested that BmPops may play an important role in balancing the molting fluid pressure to guarantee ecdysis normally. This study provides clues for further elucidating the function and regulation mechanisms of two isoforms of Bmpop gene.

Prolyl oligopeptidase (POP) is a cytosolic serine protease that hydrolyses small peptides at the carboxyl end of the proline residue. It has raised pharmaceutical interest, since its inhibitors have been shown to have antiamnesic properties. We studied prolyl oligopeptidase kinetics with two 7-amino-4-methylcoumarin derivatives: Z-Gly-Pro-AMC and Suc-Gly-Pro-AMC. Z-Gly-Pro-AMC was found to obey standard Henri-Michaelis-Menten kinetics with a K(m) of 30+/-3 microM, whereas Suc-Gly-Pro-AMC exhibited substrate inhibition kinetics with K(m) and K(is) of 510+/-150 and 270+/-90 microM, respectively. Autodock simulations revealed that either the succinyl or the AMC-end of Suc-Gly-Pro-AMC may bind to the S'1 subsite of the active site. We believe that non-specifically bound Suc-Gly-Pro-AMC allows the simultaneous binding of second substrate molecule to the active site and this leads in substrate inhibition. In addition, we demonstrated that the inhibition type of a well characterized prolyl oligopeptidase inhibitor, JTP-4819, is competitive tight binding with a K(ic) of 0.045+/-0.008 nM. We suggest that due to the high concentration of prolyl oligopeptidase in the brain (0.12 nmol/g pig brain), the tight binding nature of the inhibition should be considered when using brain homogenate as the enzyme source in prolyl oligopeptidase inhibition measurements. This is of importance in studying structure-activity relationships of potent prolyl oligopeptidase inhibitors.