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CLEAVAGE OF THE IMIDAZOLE RING IN HISTIDYL RESIDUE ANALOGUES REACTED WITH PEROXIDIZING LIPIDS
Author(s) -
YONG SAMUEL H.,
KAREL MARCUS
Publication year - 1979
Publication title -
journal of food science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.772
H-Index - 150
eISSN - 1750-3841
pISSN - 0022-1147
DOI - 10.1111/j.1365-2621.1979.tb03838.x
Subject(s) - imidazole , chemistry , residue (chemistry) , side chain , stereochemistry , ring (chemistry) , cleavage (geology) , yield (engineering) , biochemistry , organic chemistry , geotechnical engineering , fracture (geology) , engineering , polymer , materials science , metallurgy
Degradative reactions initiated by peroxidizing lipids on the histidyl imidazole side‐chain were studied by reacting the histidyl residue analogues N‐benzoylhistidine and hippurylhistidyl‐leucine with methyl linoleate in a low‐moisture model system resembling the structure of freeze‐dried foods. We found that, after incubation at 51‐57°C and 75% relative humidity for 3 wk, the imidazole side‐chain was cleaved by peroxidizing methyl linoleate to yield asparagyl and aspartyl side‐chains along with other compounds at lower concentrations. The degradation of the histidyl imidazole ring (pK a = 6.0–6.5) increased significantly at pH ≥ 7, indicating that the free base form was the labile species.