The effects of acid proteases on degradation of serum amyloid A protein (SAA) were investigated in vitro. Human recombinant SAA1 (rSAA1), when incubated with human spleen extracts at pH 3.2, was degraded in the amino‐terminal portion of the molecule. This reaction was inhibited by an acid protease inhibitor, pepstatin. The degraded SAA molecules lacking nine or more amino‐terminal residues, when exposed to in vitro fibril‐forming conditions, failed to form Congo red positive precipitates and did not show amyloid fibril‐like structure by electron microscopy. This suggests that the amino‐terminal portion of SAA is essential for fibril formation. Cathepsin D, one of the lysosomal enzymes, also initiated degradation of rSAAl at the amino‐terminus. Cathepsin D immunoreactivity was detected in marginal areas of amyloid deposits in spleens from patients with reactive amyloidosis. These findings suggest that cathepsin D or similar acid proteases may be involved in SAA catabolism and may protect against amyloid formation.
|Original language||English (US)|
|Number of pages||5|
|Journal||Scandinavian Journal of Immunology|
|State||Published - Jun 1995|
ASJC Scopus subject areas