**Author Listing - Lead/ Submitting Author (we will be communicating with this individual): Name, Institution, City and State where the work was done. Co-authors will be added in a separate section.**
Kouhei Kawaguchi, Department of Clinical Laboratory Medicine, Jichi Medical University / Applied Technology Laboratory, Eiken chemical Co., LTD., Tochigi, Japan

**Main Body of the Abstract**
【Introduction】
AA amyloidosis was caused by fibrillized and tissue deposition of the N-terminal region of serum amyloid A (SAA) as AA protein, but the mechanism is not clear. Lysosomal proteases, which degrade SAA, are believed to play a role in amyloidogenesis. In this study, we analyzed fragments of SAA digested by cathepsin D, a lysosomal protease.
【Materials and methods】
Recombinant human SAA1.1 (rSAA) at 0.2 mg/mL was incubated with cathepsin D (from human liver, 0.2 U/mL) in 50 mM sodium acetate buffer (pH 3.2) for 24 hours at 37℃.
MALDI-TOF MS analysis: The mass spectrometry was performed on a matrix-assisted laser desorption time-of-flight mass spectrometry (MALDI-TOF MS; ultrafleXtreme, Bruker Japan). Spectra were analysed by flexAnalysis (Bruker Japan). Samples were measured by linear positive mode.
【Results】
Full-length rSAA was detected at 11,813.0 m/z with a weak peak and various fragments were detected, mainly at 10,909.7 m/z, 10,539.1 m/z, 9,333.1 m/z, and 4,869.8 m/z. The fragments were estimated aa8-105, aa12-105, aa22-105, and aa63-105 based on their molecular weights.
【Discussion】
Cathepsin D generated various fragments with conserved C-terminal regions from rSAA. Therefore, cathepsin D appeared to have an inhibitory effect on AA amyloidosis. In the future, we would like to further investigate the effects of other lysosomal proteases and post-translational modifications of SAA.



**Author Listing - Lead/ Submitting Author (we will be communicating with this individual): Name, Institution, City and State where the work was done. Co-authors will be added in a separate section.**
Kouhei Kawaguchi, Department of Clinical Laboratory Medicine, Jichi Medical University / Applied Technology Laboratory, Eiken chemical Co., LTD., Tochigi, Japan

**Main Body of the Abstract**
【Introduction】
AA amyloidosis was caused by fibrillized and tissue deposition of the N-terminal region of serum amyloid A (SAA) as AA protein, but the mechanism is not clear. Lysosomal proteases, which degrade SAA, are believed to play a role in amyloidogenesis. In this study, we analyzed fragments of SAA digested by cathepsin D, a lysosomal protease.
【Materials and methods】
Recombinant human SAA1.1 (rSAA) at 0.2 mg/mL was incubated with cathepsin D (from human liver, 0.2 U/mL) in 50 mM sodium acetate buffer (pH 3.2) for 24 hours at 37℃.
MALDI-TOF MS analysis: The mass spectrometry was performed on a matrix-assisted laser desorption time-of-flight mass spectrometry (MALDI-TOF MS; ultrafleXtreme, Bruker Japan). Spectra were analysed by flexAnalysis (Bruker Japan). Samples were measured by linear positive mode.
【Results】
Full-length rSAA was detected at 11,813.0 _m/z_ with a weak peak and various fragments were detected, mainly at 10,909.7 _m/z_, 10,539.1 _m/z_, 9,333.1 _m/z_, and 4,869.8 _m/z_. The fragments were estimated aa8-105, aa12-105, aa22-105, and aa63-105 based on their molecular weights.
【Discussion】
Cathepsin D generated various fragments with conserved C-terminal regions from rSAA. Therefore, cathepsin D appeared to have an inhibitory effect on AA amyloidosis. In the future, we would like to further investigate the effects of other lysosomal proteases and post-translational modifications of SAA.



Analysis of SAA fragments digested by a lysosomal protease. PC3 (#73)

We invite you to attend the XIX International Symposium on Amyloidosis to be held in Rochester, MN.

This symposium is organized as a hybrid meeting (with the focus on in-person) held from Sunday, May 26 through Thursday, May 30, 2024.

Together with the ISA Board and members of Mayo Clinic, a very attractive scientific hybrid program is being planned. The program will cover a variety of types of systemic amyloidosis: ATTR (hereditary and wild-type), AL (light-chain), AA and less frequent forms. There will be key lectures, specific symposia including those company sponsored, oral presentations and poster sessions of accepted abstracts.

COURSE DESCRIPTION
This program will provide a comprehensive review of state-of-the-art education in systemic amyloidosis: basic science, pathophysiology, diagnosis, current and emerging treatments. Scientific presentations will include competitive oral and poster abstracts. The rapid evolution of scientific discovery and expanding treatment options has created tremendous interest in the field and this meeting will fill and important gap in educating scientists and clinicians.