Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.23.5 (cathepsin D)
 4,130 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A novel aspartic proteinase, called napsin, has recently been found in human and mouse. Due to high similarity with cathepsin D a structural model of human napsin A could be built. Based on this model a potential epitope SFYLNRDPEEPDGGE has been identified, which was used to immunize rabbits. The resulting antibody was employed in monitoring the expression of recombinant human napsin A in HEK293 cell line. Western blot analysis confirmed the specificity of the antibody and showed that human napsin A is expressed as a single chain protein with the molecular weight of approximately 38 kDa. Immunohistochemical studies revealed high expression levels of napsin A in human kidney and lung but low expression in spleen.
 ...
PMID:Human napsin A: expression, immunochemical detection, and tissue localization. 1058 Jan 6

The full-length and ectodomain forms of beta-site APP cleavage enzyme (BACE) have been cloned, expressed in Sf9 cells, and purified to homogeneity. This aspartic protease cleaves the amyloid precursor protein at the beta-secretase site, a critical step in the Alzheimer's disease pathogenesis. Comparison of BACE to other aspartic proteases such as cathepsin D and E, napsin A, pepsin, and renin revealed little similarity with respect to the substrate preference and inhibitor profile. On the other hand, these parameters are all very similar for the homologous enzyme BACE2. Based on a collection of decameric substrates, it was found that BACE has a loose substrate specificity and that the substrate recognition site in BACE extends over several amino acids. In common with the aspartic proteases mentioned above, BACE prefers a leucine residue at position P1. Unlike cathepsin D etc., BACE accepts polar or acidic residues at positions P2'0 and P1 but prefers bulky hydrophobic residues at position P3. BACE displays poor kinetic constants toward its known substrates (wild-type substrate, SEVKM/DAEFR, K(m) = 7 microm, K(cat) = 0.002 s(-1); Swedish mutant, SEVNL/DAEFR, K(m) = 9 microm, K(cat) = 0.02 s(-1)). A new substrate (VVEVDA/AVTP, K(m) = 1 microm, K(cat) = 0.004) was identified by serendipity.
 ...
PMID:Substrate and inhibitor profile of BACE (beta-secretase) and comparison with other mammalian aspartic proteases. 1174 10

Specific elution of captured proteins greatly improves the quality of proteomic data obtained from pull-downs by avoiding signals from nonspecific proteins, thus allowing more sensitive identification of target proteins. This is important in activity-based proteomics or drug target identification. However, commonly used chemically cleavable linkers can only be cleaved at close to neutral pH, which prevents them from being used for proteins binding only at lower pH when no cross-linking is applied. On the other hand, elution of common acid-cleavable labels can also coelute proteins bound by ionic interactions. Here, we report the synthesis and application of a label readily cleavable by mild oxidation at moderately acidic pH for the noncovalent labeling and pull-down of intracellular aspartic proteases. Using specific release, target proteins cathepsin D and napsin A were identified from human kidney with much higher confidence and without any nontarget hits.
 ...
PMID:A periodate-cleavable linker for functional proteomics under slightly acidic conditions: application for the analysis of intracellular aspartic proteases. 2317 76

Aspartic proteinases form a widely distributed protein superfamily, including cathepsin D, cathepsin E, pepsins, renin, BACE and napsin. Human napsin genes are located on human chromosome 19q13, which comprises napsin A and napsin B. Napsin B has been annotated as a pseudogene because it lacks an in-frame stop codon; its nascent chains are cotranslationally degraded. Until recently, there have been no studies concerning the molecular evolution of the napsin protein family in the human genome. In the present study, we investigated the evolution and gene organization of the napsin protein family. Napsin B orthologs are primarily distributed in primates, while napsin A orthologs are the only napsin genes in other species. The corresponding regions of napsin B in the available sequences from primate species contain an in-frame stop codon at a position equivalent to that of human napsin A. In addition, a rare single-nucleotide polymorphism (SNP) that creates a proper stop codon in human napsin B was identified using HapMap populations. Recombinant protein expression and three-dimensional comparative modeling revealed that napsin B exhibits residual activity toward synthetic aspartic protease substrates compared with napsin A, presumably through a napsin B-specific Arg287 residue. Thus, napsin B was duplicated from napsin A during the early stages of primate evolution, and the subsequent loss of napsin B function during primate evolution reflected ongoing human-specific napsin B pseudogenization.
 ...
PMID:Structural and phylogenetic comparison of napsin genes: the duplication, loss of function and human-specific pseudogenization of napsin B. 2333 8

Aspartic proteases are important biomarkers of human disease and interesting targets for modulation of immune response via MHC class II antigen processing inhibition. The lack of inhibitors with sufficient selectivity hampers precise analysis of the role of cathepsin E and napsin A in samples containing the ubiquitous and highly abundant homolog cathepsin D. Grassystatins from marine cyanobacteria show promising selectivity for cathepsin E but contain several ester bonds that make their synthesis cumbersome and thus limit availability of the inhibitors. Herewith, we present grassystatin-derived cathepsin E inhibitors with greatly facilitated synthesis but retained selectivity profile. We demonstrate their affinity and selectivity with both enzyme kinetic assays and streptavidin-based pull-down from cells and mouse organs. Our findings suggest that grassystatin-like inhibitors are useful tools for targeted inhibition of cathepsin E and thus provide a novel approach for cancer and immunology research.
 ...
PMID:Grassystatin-derived peptides selectively inhibit cathepsin E and have low affinity to cathepsin D. 3244 74