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) it 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 a higher correlation coefficient (r=>+0.7) for Vmax/Km compared with that (r= < ±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=> + 0.7) compared with that in the negative mode (r=<+0.5). These results suggest that MALDI-ToF MS is a useful tool to evaluate Vmax/Kmax of peptides for protein kinases.
All Science Journal Classification (ASJC) codes
- Atomic and Molecular Physics, and Optics