Heterogeneity of human amyloid protein AA and its related serum protein, SAA.

The heterogeneity of the human amyloid proteins SAA and AA was studied. Both proteins could be separated into several fractions by ion-exchange chromatography. Amino acid analysis of the ion-exchange-chromatographed fractions of protein AA showed that the main difference was in the length of the polypeptide. Thus, it seems that the original AA preparation consists of a mixture of AA proteins with length ranging from 66 to 78 amino acid residues. By enzymatic degradation of three different forms of SAA with kallikrein, fragments were formed with a molecular weight very similar to that of protein AA.