HB PETERBOROUGH [BETA-111(G13)VAL-]PHE] IN JAPAN - RAPID IDENTIFICATION BY ESI MS USING PROTEOLYTIC DIGESTS OF OXIDIZED GLOBIN/

A variant hemoglobin was found in a Japanese female whose hemoglobin w as studied to clarify the cause of a low Hb A(1c) value, found during a routine medical examination. The detection and identification of the variant was performed by electrospray ionization mass spectrometry. I ts structure was revealed to be the same as Hb Peterborough [beta 111( G13)Val-->Phe] (1). For sequence determination, oxidized globin as wel l as non-derivatized globin were cleaved by trypsin and lysyl endopept idase. An abnormal peptide was found in digests of oxidized globin, as shown by electrospray ionization mass spectrometry. Cysteic acid in o xidized peptides enhanced the abundance of fragment ions in tandem mas s spectrometry, which helped to quickly and accurately determine the s ubstitution in beta T-12, a peptide in the core region. Electrospray i onization mass spectrometry analysis of the hemolysate also showed a l ow level of glycated hemoglobin. The patient's hemolysate showed decre ased stability in the isopropanol test. An abnormal band was detected on isoelectrofocusing on the cathodic side of normal Hb A. This is the second report of Hb Peterborough and the first of its occurrence in J apan.