The reference OMIM entry for this protein is 116810

Cathepsin b; ctsb
Catb
Amyloid precursor protein secretase
App secretase; apps

CLONING

Murnane (1985) pointed out amino acid sequence homology between HRAS p21 (190020) and cathepsin B. Chan et al. (1986) cloned preprocathepsin B from hepatoma and kidney cDNA libraries. The deduced 339-amino acid preprocathepsin B contains a 17-residue N-terminal prepeptide followed by a 62-residue propeptide, 254 residues that are in the mature (single-chain) cathepsin B, and a 6-residue C-terminal extension. Human, mouse, and rat procathepsin B share at least 68% sequence identity. Moin et al. (1992) purified 3 forms of cathepsin B from normal human liver and several human tumor tissues. SDS-PAGE detected 2 forms of 25 and 26 kD that appeared as a doublet and a third form of about 30 kD. The doublet was associated with the highest cathepsin B activity. N-terminal sequencing revealed that the 25- and 26-kD forms represent the heavy chain of the mature double-chain form of cathepsin B. Endoglycosidase treatment converted the 26-kD form into the 25-kD form, suggesting that cathepsin B exists as both glycosylated and unglycosylated forms. N-terminal sequencing indicated that the 30-kD protein was the single-chain form. Using several biochemical and immunologic criteria, Moin et al. (1992) determined that the tumor and normal liver forms of cathepsin B were similar in all characteristics examined. Tam et al. (1994) isolated 2 CTSB cDNAs from a normal human embryonic fibroblast cDNA library. These clones have a 10-bp insertion in the 3-prime untranslated region (UTR) compared with the CTSB sequence reported by Chan et al. (1986). The insertion may allow the formation of a stable stem-loop structure. One of the clones reported by Tam et al. (1994) also has an extension of about 1 kb in the 3-prime UTR. Northern blot analysis using probes unique to the 3-prime UTR extension detected 4.0- and 1.7-kb CTSB transcripts, but not the major 2.2-kb transcript.

GENE STRUCTURE

Berquin et al. (1995) stated that the CTSB gene contains 12 exons. They identified 2 additional alternatively splices exons, which they designated 2a and 2b, between exons 2 and 3 in the 5-prime UTR of the CTSB gene. All of the exons of the 5-prime UTR could be alternatively spliced to produce several transcript species. In addition, there are at least 3 upstream translation initiation codons. Berquin et al. (1995) determined that the CTSB gene spans nearly 27 kb, although they suggested that it may be larger.

MAPPING

Wang et al. (1987) assigned the CTSB gene to chromosome 8p22 by means of a cDNA probe used in Southern blot analysis of somatic cell hybrids and in situ hybridization. Fong et al. (1992) mapped CTSB to 8p23.1-p22 by 3 independent methods: analysis of human-hamster somatic cell hybrid DNA by PCR, comparison of hybridization signals to cathepsin B in interphase nuclei of normal fibroblasts and fibroblasts with a chromosome 8 deletion, and fluorescence in situ hybridization. Deussing et al. (1997) mapped the Ctsb gene to mouse chromosome 14 and localized a related sequence to chromosome 2.

GENE FUNCTION

Esch et al. (1990) demonstrated cleavage of the amyloid beta peptide during constitutive processing of its precursor (APP; 104760). Cleavage occurs in the interior of the amyloid peptide sequence, thereby precluding formation and deposition of the APP protein. Esch et al. (1990) suggested that a genetic defect in this processing mechanism might be a basis of Alzheimer disease (104300). Tagawa et al. (1991) demonstrated t ... More on the omim web site

Subscribe to this protein entry history

March 3, 2020: Protein entry updated
Automatic update: Entry updated from uniprot information.

Dec. 9, 2018: Protein entry updated
Automatic update: Entry updated from uniprot information.

Oct. 19, 2018: Protein entry updated
Automatic update: OMIM entry 116810 was added.

Oct. 19, 2018: Additional information
Initial protein addition to the database. This entry was referenced in Bryk and co-workers. (2017).