title: A dual fluorescent/MALDI chip platform for analyzing enzymatic activity and for protein profiling.
abstract: Being able to rapidly and sensitively detect specific enzymatic products is important when screening biological samples for enzymatic activity. We present a simple method for assaying protease activity in the presence of protease inhibitors (PIs) by measuring tryptic peptide accumulation on copolymer pMALDI target chips using a dual fluorescence/MALDI-TOF-MS read-out. The small platform of the chip accommodates microliter amounts of sample and allows for rapid protein digestion. Fluorescamine labeling of tryptic peptides is used to indicate the proteolytic activity and is shown to be an affordable, simple process, yielding a strong fluorescence signal with a low background. Subsequent MALDI-TOF-MS analysis, performed in the same sample well, or in a parallel well without adding fluorescamine, detects the specific tryptic peptides and provides confidence in the assay. The dual read-out method was applied to screen the inhibition activity of plant PIs, components of plant defense against herbivores and pathogens. Extracts of PIs from Solanum nigrum and trypsin were applied together to a pMALDI chip on which a suitable substrate was adsorbed. The fluorescence and MALDI-TOF-MS signal decrease were associated with the inhibitory effect of the PIs on trypsin. The developed platform can be modified to screen novel protease inhibitors, namely, those potentially useful for treating or preventing infection by viruses, including HIV and hepatitis C.
authors.affiliation: Mass Spectrometry Research Group, Max Planck Institute for Chemical Ecology, Jena, Germany.
authors.forename: Vincentius A
authors.initials: VA
authors.lastname: Halim
authors.forename: Alexander
authors.initials: A
authors.lastname: Muck
authors.forename: Markus
authors.initials: M
authors.lastname: Hartl
authors.forename: Alfredo J
authors.initials: AJ
authors.lastname: Ibáñez
authors.forename: Ashok
authors.initials: A
authors.lastname: Giri
authors.forename: Florian
authors.initials: F
authors.lastname: Erfurth
authors.forename: Ian T
authors.initials: IT
authors.lastname: Baldwin
authors.forename: Ales
authors.initials: A
authors.lastname: Svatos
mesh_terms: D005450:Fluorescamine / Q000737:chemistry; D010447:Peptide Hydrolases / Q000032:analysis* / Q000378:metabolism*; D010455:Peptides / Q000378:metabolism; D010940:Plant Proteins / Q000032:analysis / Q000378:metabolism; D011480:Protease Inhibitors / Q000032:analysis / Q000378:metabolism; D040081:Protein Array Analysis / Q000295:instrumentation / Q000379:methods*; D012273:Ribulose-Bisphosphate Carboxylase / Q000378:metabolism; D012710:Serum Albumin, Bovine / Q000378:metabolism; D032324:Solanum nigrum / Q000201:enzymology*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000295:instrumentation / Q000379:methods; D014357:Trypsin / Q000378:metabolism
chemical_list: D010455:Peptides; D010940:Plant Proteins; D011480:Protease Inhibitors; D012710:Serum Albumin, Bovine; D005450:Fluorescamine; D010447:Peptide Hydrolases; D014357:Trypsin; D012273:Ribulose-Bisphosphate Carboxylase