Facile degradation of apolipoprotein B by radical reactions and the presence of cleaved proteins in serum

A facile cleavage of peptide bonds of apolipoprotein B (apoB) by radical re action is reported, When human LDL was subjected to oxidative damage using Cu2+, extensive degradation of apoB was observed based on immunoblotting, T he degradation of apoB was inhibited by radical scavengers (beta-mercaptoet hanol, butylated hydroxytoluene, and probucol) and promoted by a radical in itiator [2,2'-azobis(2-amidinopropane)dihydrochloride], When human serum wa s treated with Cu2+, a similar cleavage pattern of apoB was observed. The c leaved apoB proteins were also detected in normal serum on the basis of imm unoblots, These results suggest that apoB is highly reactive toward radical s in vitro and in vivo, with reaction resulting in the cleavage of peptide bonds.