Chemically Modified, Immobilized Trypsin Reactor with Improved Digestion Efficiency

Tryptic digestion followed by identification using mass spectrometry is an important step in many proteomic studies. Here, we describe the preparation of immobilized, acetylated trypsin for enhanced digestion efficacy in integrated protein analysis platforms. Complete digestion of cytochrome c was o...

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Bibliographic Details
Published in:Journal of proteome research 2005-09, Vol.4 (5), p.1805-1813
Main Authors: Freije, J. Robert, Mulder, Patty P. M. F. A, Werkman, Wendy, Rieux, Laurent, Niederlander, Harm A. G, Verpoorte, Elisabeth, Bischoff, Rainer
Format: Article
Language:English
Subjects:
Acetonitriles - chemistry
Acetonitriles - pharmacology
Acetylation
Amino Acid Sequence
Animals
Catalysis
Cattle
Chromatography, High Pressure Liquid
Cytochromes c - chemistry
Horses
Kinetics
Mass Spectrometry - methods
Molecular Sequence Data
Myoglobin - chemistry
Peptide Mapping
Proteins - chemistry
Proteome
Proteomics - methods
Sequence Homology, Amino Acid
Substrate Specificity
Time Factors
Trypsin - chemistry
Trypsin - pharmacology
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Summary:Tryptic digestion followed by identification using mass spectrometry is an important step in many proteomic studies. Here, we describe the preparation of immobilized, acetylated trypsin for enhanced digestion efficacy in integrated protein analysis platforms. Complete digestion of cytochrome c was obtained with two types of modified-trypsin beads with a contact time of only 4 s, while corresponding unmodified-trypsin beads gave only incomplete digestion. The digestion rate of myoglobin, a protein known to be rather resistant to proteolysis, was not altered by acetylating trypsin and required a buffer containing 35% acetonitrile to obtain complete digestion. The use of acetylated-trypsin beads led to fewer interfering tryptic autolysis products, indicating an increased stability of this modified enzyme. Importantly, the modification did not affect trypsin's substrate specificity, as the peptide map of myoglobin was not altered upon acetylation of immobilized trypsin. Kinetic digestion experiments in solution with low-molecular-weight substrates and cytochrome c confirmed the increased catalytic efficiency (lower K M and higher k cat) and increased resistance to autolysis of trypsin upon acetylation. Enhancement of catalytic efficiency was correlated with the number of acetylations per molecule. The favorable properties of the new chemically modified trypsin reactor should make it a valuable tool in automated protein analysis systems. Keywords: immobilized trypsin • digestion reactors • chemical modification • acetylation • proteomics
ISSN:1535-3893
1535-3907
DOI:10.1021/pr050142y