title: Letter: correlation between phosphorylation ratios by matrix-assisted laser desorption/ionization time-of-flight mass spectrometric analysis and enzyme kinetics.
abstract: To identify the correlation between the phosphorylation ratios by matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry (MALDI-ToF MS) analysis and enzyme kinetics (Km, Vmax, and Vmax/Km) is important to understand whether MALDI-TOF MS can be applied for monitoring the properties of peptides that are substrates of protein kinases. The correlation between phosphorylation ratios and enzyme kinetics was examined using peptides for protein kinase C (PKC) and for 60 kDa phosphoprotein, encoded by the cellular sarcoma gene (c-Src). Phosphorylation ratios, analyzed by MALDI-ToF MS, showed higher correlation coefficient (r = or > +0.7) for Vmax/Km compared with that (r = or < -/+0.6) for Km or Vmax. For ion modes, a higher correlation coefficient between phosphorylation ratios and Vmax/Km was identified in the positive mode (r = or > +0.7) compared to that in the negative mode (r = or < +0.5). These results suggest that MALDI-ToF MS is a useful tool to evaluate Vmax/Km of peptides for protein kinases.
authors.affiliation: Department of Applied Chemistry, Faculty of Engineering, Kyushu University, 744 Motooka, Nishi-Ku, Fukuoka 819-0395, Japan. jrjhkangtcm@mbox.nc.kyushu-u.ac.jp
authors.forename: Jeong-Hun
authors.initials: JH
authors.lastname: Kang
authors.forename: Masanori
authors.initials: M
authors.lastname: Kuramoto
authors.forename: Akira
authors.initials: A
authors.lastname: Tsuchiya
authors.forename: Riki
authors.initials: R
authors.lastname: Toita
authors.forename: Daisuke
authors.initials: D
authors.lastname: Asai
authors.forename: Yuko T
authors.initials: YT
authors.lastname: Sato
authors.forename: Takeshi
authors.initials: T
authors.lastname: Mori
authors.forename: Takuro
authors.initials: T
authors.lastname: Niidome
authors.forename: Yoshiki
authors.initials: Y
authors.lastname: Katayama