Identification of Human Liver Diacetyl Reductases by Nano-Liquid Chromatography/Fourier Transform Ion Cyclotron Resonance Mass Spectrometry

✍ Scribed by Yorihisa Tanaka; Ikuya Sato; Chisaki Iwai; Toshiyuki Kosaka; Toshihiko Ikeda; Takemichi Nakamura

• Publisher: Elsevier Science
• Year: 2001
• Tongue: English
• Weight: 238 KB
• Volume: 293
• Category: Article
• ISSN: 0003-2697
• DOI: 10.1006/abio.2001.5128

✦ Synopsis

Several forms of diacetyl-reducing enzyme were found to exist in the human liver cytosol. Three (DAR-2, DAR-5, and DAR-7) of them were purified as a single band on SDS-PAGE by a combination of a few kinds of column chromatographies. The in-gel tryptic digests of the purified enzymes were analyzed by nano-liquid chromatography (LC)/Fourier transform ion cyclotron resonance mass spectrometry (FT ICR MS), which provided peptide masses at a ppm-level accuracy. The enzymes, DAR-2, DAR-5, and DAR-7, were identified as alcohol dehydrogenase ␤ subunit (ADH2), carbonyl reductase (CBR1), and aldehyde reductase (AKR1A1), respectively, by peptide mass fingerprinting. In addition, an alternating-scan acquisition of nano-LC/FT ICR mass spectra, i.e., switching of normal acquisition conditions and in-source fragmentation conditions scan by scan, provided sets of parent and fragment ion masses of many of the tryptic peptides in a single LC/MS run. The peptide sequence-tag information at the ppm-level accuracy was used to further confirm the protein identities. It was demonstrated that nano-LC/FT ICR MS can be used for rigorous protein identification at a subpicomole level as an alternative technique to nano-LC/MS/MS.