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Enzymic properties of recombinant BACE2.
Yong-Tae Kim1, Deborah Downs, Shili Wu
1Functional Proteomics Laboratory and Crystallography Program, Oklahoma Medical Research Foundation, Oklahoma City, OK 73104, USA.
European Journal of Biochemistry
|November 9, 2002
Summary
Beta-secretase 2 (BACE2) is an aspartic protease with distinct enzymatic properties from BACE1, the enzyme linked to Alzheimer's disease. Research reveals BACE2 exhibits broad pH activity and unique substrate specificities, suggesting varied physiological roles.
Area of Science:
- Biochemistry
- Enzymology
- Molecular Biology
Background:
- Beta-secretase 2 (BACE2), also known as Memapsin 1, is a membrane-bound aspartic protease homologous to BACE1 (Memapsin 2).
- While BACE1 is implicated in Alzheimer's disease (AD) through amyloid precursor protein (APP) processing, BACE2's physiological functions and direct role in APP metabolism are not established.
- BACE2 is expressed in vivo as a precursor protein with multiple domains, including pre-, pro-, protease, transmembrane, and cytosolic regions.
Purpose of the Study:
- To elucidate the enzymatic properties of BACE2.
- To characterize two recombinant variants of the pro-BACE2 protease domain (pro-BACE2-T1 and pro-BACE2-T2) to understand their substrate specificities and activity profiles.
- To investigate the potential processing of pro-BACE2 by BACE1.
Main Methods:
- Construction and expression of two recombinant pro-BACE2 variants (pro-BACE2-T1 and pro-BACE2-T2) in Escherichia coli.
- Refolding and purification of the recombinant proteins.
- Enzymatic assays to determine substrate specificities and activity across a range of pH conditions.
Main Results:
- Recombinant pro-BACE2-T1 exhibited substrate specificities similar to BACE1 and other general aspartic proteases.
- Pro-BACE2-T2 displayed a more constrained specificity, preferentially cleaving adjacent to paired basic residues.
- Unlike typical aspartic proteases active only at acidic pH, recombinant BACE2 (pro-BACE2-T1) demonstrated activity over a broad pH range.
- BACE1 was shown to process pro-BACE2 at its in vivo maturation site.
Conclusions:
- BACE2 possesses distinct enzymatic characteristics, including broad pH activity and varied substrate preferences, differentiating it from BACE1.
- The differential substrate specificities of BACE2 variants suggest diverse physiological roles beyond APP processing.
- The interaction between BACE1 and BACE2, with BACE1 processing pro-BACE2, indicates a potential regulatory relationship between these enzymes.