Four variants of human plasma Zn-alpha 2-glycoprotein (ZAG) in the Japanese population

Zn-alpha 2-glycoprotein (ZAG) of plasma from the general Japanese adult population (n = 1224) was studied by polyacrylamide gel isoelectric focusing (IEF) followed by immunoblotting with specific antiserum to ZAG. Most of the plasmas showed a common band pattern, while 16 samples showed four other patterns. These ZAG band patterns were easily differentiated by desialyzing the samples prior to IEF. The asialo form of ZAG commonly showed a single band. The 16 plasma samples presenting double bands were classified into four types containing the common single band. The differences in ZAG phenotypes may be suggested to be due to amino acid substitutions of the ZAG molecule. The statistical frequencies of five alleles, which we proposed to designate ZAG*1, ZAG*2, ZAG*3, ZAG*4, and ZAG*5, were 0.9935, 0.0025, 0.0016, 0.0004, and 0.0020, respectively. The genetic transmission of the rare alleles ZAG*3 and ZAG*4 was confirmed by two family studies.