[Show abstract][Hide abstract] ABSTRACT: A novel mass spectrometry-based assay system for determining protein kinase activity employing mass-tagged substrate peptide probes was used for the diagnosis of tumors. Two peptide probes (H-type and D-type) were synthesized containing the same substrate peptide sequence for protein kinase C (PKC). The molecular weights of the two probes differ because of the incorporation of deuterium into the acetyl groups of the D-type probe. The lysates of the normal and tumor tissue were prepared and reacted with the H- and D-type peptide probes, respectively. The PKC activities of the normal and tumor tissues can be compared simply and directly by calculating the phosphorylated ratio to each peptide probe, obtained from the peak intensity of the mass spectrum after mixing of the two reaction solutions. The phosphorylation ratio for the reaction of the H-type peptide probe with the tumor tissue lysate (B16 melanoma) was more than three times higher than that of the D type peptide probe with the normal skin tissue lysate. These results show that the novel assay system for detecting protein kinase activity using mass-tag technology can be a simple and useful means to profile protein kinase activity for cell or tissue lysate samples, and can be applied to the diagnosis of tumors.
Full-text · Article · Feb 2007 · Journal of the American Society for Mass Spectrometry
[Show abstract][Hide abstract] ABSTRACT: An intracellular signal transduction system involved in many kinds of proteins regulates various cellular events, such as cellular proliferation, differentiation and cell death, responding to the outer environment. Among those proteins, protein kinases are one of the most important class of proteins. It has been reported that abnormal activities of protein kinases are related to various diseases. Therefore, an analysis of protein kinase activity would be useful for diagnosis and drug screening. Herein, we describe the detection of on-chip phosphorylation using a peptide chip by fluorescence imaging. In this work, we selected a cAMP-dependent protein kinase (PKA) as a model, and quantitatively evaluated the substrate specificity for PKA using a peptide chip. Moreover, we attempted to detect intracellular kinase activity. Since src correlates with breast cancer, we measured the src activity in MCF-7 human breast cancer cell lysate. Consequently, with our peptide chip we could detect the src activity in MCF-7 cell lysate. Therefore, this method could be applied to diagnosis, drug discovery and screening.