1. Inhibition of cruzipain visualized in a fluorescence quenched solid-phase inhibitor library assay. D-amino acid inhibitors for cruzipain, cathepsin B and cathepsin L
M Meldal, I B Svendsen, L Juliano, M A Juliano, E D Nery, J Scharfstein J Pept Sci. 1998 Apr;4(2):83-91. doi: 10.1002/(sici)1099-1387(199804)4:23.0.co;2-z.
A PEGA-resin was derivatized with a 3:1 mixture of hydroxymethyl benzoic acid and Fmoc-Lys(Boc)-OH and the fluorogenic substrate Ac-Y(NO2)KLRFSKQK(Abz)-PEGA was assembled on the lysine using the active ester approach. Following esterification of the hydroxymethyl benzoic acid with Fmoc-Val-OH a library XXX-k/r-XXXV containing approximately 200,000 beads was assembled by split synthesis. The resulting 'one bead, two peptides' library was subjected to extensive hydrolysis with cruzipain. One hundred darker beads were isolated and the 14 most persistently dark beads were collected and sequenced. The putative inhibitor peptides and several analogues were synthesized and found to be competitive microM to nM inhibitors of cruzipain in solution. The inhibitory activity was found to be unspecific to cruzipain when compared with cathepsins B and L and specific when compared with kallikrein. One of the inhibitors was docked into the active site of cathepsin B and was found most probably to bind to the enzyme cavity in an unusual manner, owing to the inserted D-amino acid residue.
2. Comparison of modification sites in glycated crystallin in vitro and in vivo
Martyna Kielmas, Monika Kijewska, Alicja Kluczyk, Jolanta Oficjalska, Bożena Gołębiewska, Piotr Stefanowicz, Zbigniew Szewczuk Anal Bioanal Chem. 2015 Mar;407(9):2557-67. doi: 10.1007/s00216-015-8487-7. Epub 2015 Jan 31.
Glycation of α-crystallin is responsible for age- and diabetic-related cataracts, which are the main cause of blindness worldwide. We optimized the method of identification of lysine residues prone to glycation using the combination of LC-MS, isotopic labeling, and modified synthetic peptide standards with the glycated lysine derivative (Fmoc-Lys(i,i-Fru,Boc)-OH). The in vitro glycation of bovine lens α-crystallin was conducted by optimized method with the equimolar mixture of [(12)C6]- and [(13)C6]D-glucose. The in vivo glycation was studied on human lens crystallin. The glycated protein was subjected to proteolysis and analyzed using LC-MS. The results of in vitro and in vivo glycation of α-crystallin reveal a different distribution of the modified lysine residues. More Amadori products were detected as a result of the in vitro reaction due to forced glycation conditions. The developed method allowed us to identify the glycation sites in crystallin from eye lenses obtained from patients suffering from the cataract. We identified K166 in the A chain and K166 in the B chain of α-crystallin as major glycation sites during the in vitro reaction. We found also two in vivo glycated lysine residues: K92 in the B chain and K166 in the A chain, which are known as locations for Amadori products. These modification sites were confirmed by the LC-MS experiment using two synthetic standards. This study demonstrates the applicability of the LC-MS methods combined with the isotopic labeling and synthetic peptide standards for analysis of post-translational modifications in the biological material.
3. DNA binding behavior of peptides carrying acridinyl units: First example of effective poly-intercalation
H Ueyama, M Takagi, M Waki, S Takenaka Nucleic Acids Res Suppl. 2001;(1):163-4. doi: 10.1093/nass/1.1.163.
Bis-, tris-, tetrakis-, and pentakis-acridinyl (Acr) peptides 2-5 were synthesized from Fomc-Lys(Acr)-OH and Fmoc-Lys(Boc)-OH with the peptide synthesizer. The molar absorptivity of these peptides saturated with an increase in the number of the acridinyl unit in the peptide, suggesting intramolecular stacking of the acridinyl units. It was found from Scatchard analysis by means of spectrophotometry that all the peptides can bind to double stranded DNA with very high affinity even under high salt conditions (0.4 M NaCl) and the logarithmic binding constant increased in proportion to the number of the acridinyl unit in the peptide. This result suggested effective poly-intercalation of all the acridinyl units into double stranded DNA.
