Mapping of proteins in human saliva using two-dimensional gel electrophoresis and peptide mass fingerprinting

Human saliva contains a large number of proteins that can be used for diagnosis and are of great potential in clinical and epidemiological research. The aim of this work was to map the proteins in saliva by two-dimensional gel electrophoresis (2-DE), and to identify abundant proteins by peptide mass fingerprinting using trypsin cleavage and matrix-assisted laser desorption/ionization-time of flight-mass spectrometry analysis. One hundred proteins were identified representing 20 different identities according to accession numbers. Abundant proteins expressed in different forms were: alpha-amylase, immunoglobulin A, prolactin-inducible protein, zinc-alpha(2)-glycoprotein and cystatins (S, SA, D and SN). Other proteins found were interleukin-1 receptor antagonist, von Ebner's gland protein (lipocalin-1) and calgranulin A and B (S100A8 and A9). Furthermore, apolipoprotein A-I, beta(2)-microglobulin, glutathione S-transferase P and fatty acid-binding protein were also identified. Our results show that human saliva contains a large number of proteins that are involved in inflammatory and immune responses. The 2-DE protein map constructed opens the possibility to investigate protein changes associated with disease processes.