PEPTIDE QUANTIFICATION BY TANDEM MASS-SPECTROMETRY

This manuscript reviews the literature on the mass spectrometry (MS) a nd tandem mass spectrometry (MS/MS) quantification of biologically imp ortant peptides that have been extracted from tissues. The most import ant aspect of this quantification process is the use of MS/MS to link the protonated molecule ion, (M + H)(+), of the peptide with one or mo re of its amino acid sequence-determining fragment ions. The actual na me of a peptide cannot be used in any study until the amino acid seque nce of that peptide has been firmly established. This article reviews the analytical data obtained from the measurement of opioid peptides i n human pituitary tissues. For example, the proopiomelanocortin (POMC) -derived beta-endorphin (BE) and the proenkephalin A-derived methionin e enkephalin (ME) opioid peptides have been quantified. The biogenesis of opioid neuropeptides is briefly reviewed, critical aspects of pitu itary neuropeptides are discussed, including their localization and re gulation, and their role in tumor formation; other analytical methods used to detect and measure neuropeptides are mentioned, including radi oimmunoassay (RIA), radioreceptorassay (RRA), in situ hybridization, m RNA, and cDNA methods, and the MS and MS/MS methods are described. The use of stable isotope-incorporated synthetic peptide internal standar ds is described. Data are presented on the measurement of BE and ME in control pituitaries and in pituitary tumors (PRL-secreting and nonsec reting tumors). A significant alteration in the POMC peptide BE was fo und between the control and tumor tissues. That difference suggests th at the POMC neuropeptidergic system had been down-regulated in those t umors. (C) 1997 John Wiley & Sons, Inc.