Biochemical characterization of bovine alpha-fetoprotein and comparison with human alpha-fetoprotein

This study compares the molecular, charge and lectin microheterogeneity of bovine alpha-fetoprotein (bAFP) with human (h) AFP. Molecular weights of bAFP (81 kDa) and hAFP (69 kDa) were detected by Western immunoblotting. Marked crossreactivity was found between bAFP and hAFP by Western immunoblotting but no crossreactivity was noticed by radioimmunoassays. At least seven charge isoforms of bAFP and three isoforms of hAFP were consistently detected by chromatofocusing in a mixture of fetal bovine serum (FBS) and human cord blood (hCB), while only three isoforms of bAFP and hAFP were detected in a mixture of bovine (bAF) and human amniotic fluid (hAF). Using concanavalin A (Con A) chromatography, 50% of bAFP was Con A reactive and 50% non-reactive, while more than 98% of hAFP was Con A reactive in a mixture of FBS and hCB. However, in AFs, 72% of bAFP was Con A reactive, while 89% of hAFP was Con A reactive. These data indicate that marked differences exist in both the charge and lectin microheterogeneity of bovine and human AFP.