Serum Amyloid A (SAA) — The Precursor of Protein AA in Secondary Amyloidosis
In 1968, Prasandco-workers (1) published the water extraction technique which has become the standard method for purification of amyloidfibrils. Subsequent gel filtration of dissociated fibrils obtained from different clinical and experimental types of amyloidosis has in many instances revealed an elution pattern consisting of two main protein peaks (2). The second of these peaks represents a protein with molecular weight ranging from 4.2 to 31 kD in different amyloid preparations (2). It is the recognition and characterization of this low molecular weight amyloid protein that has enabled a chemical and immunologic classification of amyloid fibrils (2,3). It has been shown that different, apparently non related proteins can constitute the fibrils sub unit is different cases of amyloidosis. Moreover, the nature of the protein is in most cases related to specific clinical types of amyloidosis (2,3). Certain serum proteins are precursors for the different fibril proteins in the various systemic forms of amyloidosis (2,3). Two important fibril proteins related to systemic amyloidosis are the amyloidL (AL) and amyloid A (AA) proteins. Protein AL, which consists of homogenous (monoclonal) immunoglobulin kappa or lambda light chains or fragments thereof (2,3) are seen in primary (idiopathic) and myeloma-associated amyloidosis (ALamyloidosis). Protein AA is associated with secondary (reactive) amyloidosis, the recessively inherited familial Mediterranean fever (FMF), and spontaneous and experi-mental amyloidosis in animals (2,3). These forms of amyloidosis can there-fore, also be called AA amyloidosis. This presentation will concentrate on protein AA and its serum precursor SAA.
KeywordsFamilial Mediterranean Fever Amyloid Fibril Serum Amyloid Amyloid Protein Secondary Amyloidosis
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