title: Ambient Ionization Mass Spectrometry Measurement of Aminotransferase Activity.
abstract: A change in enzyme activity has been used as a clinical biomarker for diagnosis and is useful in evaluating patient prognosis. Current laboratory measurements of enzyme activity involve multi-step derivatization of the reaction products followed by quantitative analysis of these derivatives. This study simplified the reaction systems by using only the target enzymatic reaction and directly detecting its product. A protocol using paper spray mass spectrometry for identifying and quantifying the reaction product has been developed. Evaluation of the activity of aspartate aminotransferase (AST) was chosen as a proof-of-principle. The volume of sample needed is greatly reduced compared with the traditional method. Paper spray has a desalting effect that avoids sprayer clogging problems seen when examining serum samples by nanoESI. This very simple method does not require sample pretreatment and additional derivatization reactions, yet it gives high quality kinetic data, excellent limits of detection (60 ppb from serum), and coefficients of variation <10% in quantitation. Graphical Abstract ᅟ.
authors.affiliation: Department of Chemistry, Purdue University, West Lafayette, IN, USA. xiny@stanford.edu.|Department of Chemistry, Stanford University, Stanford, CA, USA. xiny@stanford.edu.
authors.forename: Xin
authors.identifier: 0000-0002-8292-130X
authors.initials: X
authors.lastname: Yan
authors.affiliation: Department of Chemistry, Purdue University, West Lafayette, IN, USA.
authors.forename: Xin
authors.initials: X
authors.lastname: Li
authors.affiliation: Department of Chemistry, Purdue University, West Lafayette, IN, USA.
authors.forename: Chengsen
authors.initials: C
authors.lastname: Zhang
authors.affiliation: Department of Chemistry, Purdue University, West Lafayette, IN, USA.|College of Life Sciences, Jilin University, Changchun, China.
authors.forename: Yang
authors.initials: Y
authors.lastname: Xu
authors.affiliation: Department of Chemistry, Purdue University, West Lafayette, IN, USA. cooks@purdue.edu.
authors.forename: R Graham
authors.initials: RG
authors.lastname: Cooks
mesh_terms: D001219:Aspartate Aminotransferases / Q000032:analysis / Q000097:blood / Q000378:metabolism; D002138:Calibration; D018698:Glutamic Acid / Q000032:analysis; D006801:Humans; D013058:Mass Spectrometry / Q000295:instrumentation / Q000379:methods* / Q000592:standards; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods; D000637:Transaminases / Q000032:analysis / Q000378:metabolism*
chemical_list: D018698:Glutamic Acid; D000637:Transaminases; D001219:Aspartate Aminotransferases
keywords: Clinical enzymology; Diagnostics; Enzyme activity; Kinetics; Liver Disease; Multiple reaction monitoring; Paper spray; Point-of-care measurements