Fetal Sığır Serum Asetilkolinesterazının Tetramerik Yapısını Organize Eden Poliprolin Peptidlerin Kütle Spektrometre ile Analizi
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Acetylcholinesterase (AChE) in the serum of fetal bovine is a tetrameric enzyme. The related enzyme, butyrylcholinesterase (BChE), in the sera of humans and horse requires polyproline peptides for assembly into tetramers. The goal of this study was to determine whether soluble tetrameric AChE includes tetramer organizing peptides in its structure. In this study, fetal bovine serum AChE was denatured by boiling to release non-covalently bound peptides. Released peptides were separated from bulk protein by filtration and by high performance liquid chromatography. Peptide mass and amino acid sequence of the released peptides were determined by MALDI–TOF–TOF and LTQ-Orbitrap mass spectrometry. Fourteen polyproline peptides, divided into 5 families, were identified. The longest peptide contained 25 consecutive prolines and no other amino acid. Other polyproline peptides included one nonproline amino acid. A search of the mammalian proteome database suggested that this assortment of polyproline peptides originated from at least 5 different precursor proteins, none of which were the ColQ or PRiMA of membrane-anchored AChE. To date, AChE and BChE are the only proteins known that include polyproline tetramer organizing peptides in their tetrameric structure.