Catalysis of the hydrolysis of nonterminal peptide bonds in a polypeptide chain by a mechanism using a cysteine residue at the enzyme active center, and requiring the presence of calcium.
The whole of the physical, chemical, and biochemical processes carried out by multicellular organisms to break down ingested nutrients into components that may be easily absorbed and directed into metabolism.
In the course of the genomic cloning of nCL-2, a stomach-specific calpain, we identified a genomic clone encoding a novel member of the calpain large subunit family and designated it 'nCL-4'. First, using exon sequences, we cloned the cDNA for mouse nCL-4. Based on this sequence, we also cloned the cDNAs for rat and human nCL-4. In the case of human nCL-4, the longest open reading frame encodes 690 amino acid residues (Mr 79095) with equal sequence similarities (50-55%) to both ubiquitous and organ-specific calpain large subunits from mammals. The deduced amino acid sequence revealed that nCL-4 is highly conserved among mammals. nCL-4 can be aligned without significant deletions or insertions, and, thus, like other calpains, can be divided into four domains (I-IV). The significant similarity of domains II and IV to those in conventional calpain large subunits suggests the potential protease activity and Ca2+-binding ability of nCL-4. Northern blot analysis revealed that the mRNA for nCL-4 is expressed predominantly in stomach and small intestine but not in uterus, suggesting specialized functions of nCL-4 in the digestive tract. When overexpressed in COS-7 cells, a specific band for nCL-4 was detected. In addition, the gene coding for nCL-4 was localized on human chromosome 1.
Enzyme which catalyzes hydrolysis reaction, i.e. the addition of the hydrogen and hydroxyl ions of water to a molecule with its consequent splitting into two or more simpler molecules.
Proteolytic enzyme with a cysteine residue (Cys) in its active site. There are many families of thiol proteases. The most well known one is the papain family (C1 in MEROPS classification) which is known to exist in most eukaryotes.
A reference proteome is a set of protein sequences derived from a complete proteome which constitutes a defined standard for a particular user community. Reference proteomes are manually defined according to a number of criteria. They cover the proteomes of well- studied model organisms and other proteomes of interest for biomedical and biotechnological research. Reference proteomes have been selected to provide broad coverage of the tree of life, and constitute a representative cross-section of the taxonomic diversity to be found within UniProtKB.
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