N-terminal glycation of proteins and peptides in foods and in vivo: evaluation of N-(2-furoylmethyl)valine in acid hydrolyzates of human hemoglobin.
Specific determination of N-(2-furoylmethyl)valine (FM-Val) together with furosine in acid hydrolyzates of human hemoglobin of healthy volunteers (n = 6) and diabetic patients (n = 14) by means of reversed-phase HPLC with electrospray ionization-time-of-flight mass spectroscopy is reported. Whereas FM-Val is formed during acid hydrolysis of the N-terminal hemoglobin adduct N-fructosylvaline, furosine results from acid degradation of lysine residues glycated at the epsilon-amino group. Quantification was based on the use of synthesized isotopomers, namely N-[2-(13C6)furoylmethyl]valine and N-epsilon-[2-(13C6)furoylmethyl]lysine, thus enabling interference-free detection and calibration. Taking the conversion factors into account, the amount of N-terminally bound N-fructosylvaline in human hemoglobin was between 518 and 774 pmol/mg protein for healthy volunteers and between 586 and 1426 pmol/mg protein for diabetic patients. Derivatization at the side chain of peptide-bound lysine residues to N-epsilon-fructosyllysine was from 1156 to 1753 pmol/mg protein for healthy controls and from 1191 to 2409 pmol/mg protein for diabetics. For these patients, the amount of N-fructosylvaline showed good correlation with the values for HbA(1c). The significantly higher relative extent of glycation at the N terminus compared to side-chain glycation points to a specific and intraindividual capacity for enzymatic deglycation in human erythrocytes, which can be assessed using the proposed method.
Penndorf
Ilka
I
Institute of Food Chemistry, Technische Universität Dresden, D-01062 Dresden, Germany.
Li
Changhao
C
Schwarzenbolz
Uwe
U
Henle
Thomas
T
D001798:Blood Proteins / Q000737:chemistry; D002851:Chromatography, High Pressure Liquid; D005504:Food Analysis; D006442:Glycated Hemoglobin / Q000032:analysis; D017127:Glycation End Products, Advanced; D006454:Hemoglobins / Q000737:chemistry*; D006801:Humans; D008239:Lysine / Q000031:analogs & derivatives / Q000032:analysis; D010455:Peptides / Q000737:chemistry*; D011506:Proteins / Q000737:chemistry*; D021241:Spectrometry, Mass, Electrospray Ionization; D014633:Valine / Q000031:analogs & derivatives* / Q000032:analysis*
D001798:Blood Proteins; D006442:Glycated Hemoglobin; D017127:Glycation End Products, Advanced; D006454:Hemoglobins; D008239:Lysine; D010455:Peptides; D011506:Proteins; D014633:Valine; C530566:N-(2-furoylmethyl)valine; C033186:fructosyl-lysine