SERUM AMYLOID-A (SAA) - AN ACUTE-PHASE PROTEIN AND APOLIPOPROTEIN

Serum amyloid A (SAA) proteins comprise a family of apolipoproteins co ded for by at least three genes with allelic variation and a high degr ee of homology between species. The synthesis of certain members of th e family is greatly increased in inflammation. However, SAA is not oft en used as an acute-phase marker despite being at least as sensitive a s C-reactive protein. SAA proteins can be considered as apolipoprotein s since they associate with plasma lipoproteins mainly within the high density range, perhaps through amphipathic alpha-helical structure. I t is not known why certain subjects expressing SAA develop secondary s ystemic amyloidosis. There is still no specific function attributed to SAA; however, a popular hypothesis suggests that SAA may modulate met abolism of high density lipoproteins (HDL). This may impede the protec tive function of HDL against the development of atherosclerosis. The p otential significance of the association between SAA and lipoproteins needs further evaluation.