DB code: S00444

RLCP classification 1.13.30000.44 : Hydrolysis
CATH domain : Cathepsin B; Chain A Catalytic domain

CATH domain Related DB codes (homologues) : Cathepsin B; Chain A S00445 S00447 S00448 S00449 S00450 S00451 S00446 S00518

Uniprot Enzyme Name
UniprotKB Protein name Synonyms RefSeq MEROPS Pfam
Q9UBR2 Cathepsin Z
Cathepsin X
Cathepsin P
NP_001327.2 (Protein)
NM_001336.3 (DNA/RNA sequence)
C01.013 (Cysteine)
PF00112 (Peptidase_C1)
[Graphical View]

KEGG enzyme name
cathepsin X
cathepsin B2
cysteine-type carboxypeptidase
cathepsin IV
cathepsin Z
acid carboxypeptidase
lysosomal carboxypeptidase B

UniprotKB: Accession Number Entry name Activity Subunit Subcellular location Cofactor
Q9UBR2 CATZ_HUMAN Release of C-terminal amino acid residues with broad specificity, but lacks action on C-terminal proline. Shows weak endopeptidase activity. Lysosome.

KEGG Pathways
Map code Pathways E.C.

Compound table
Substrates Products Intermediates
KEGG-id C00012 C00001 C00045 C00012
Compound Peptide H2O Amino acid Peptide
Type peptide/protein H2O amino acids peptide/protein
ChEBI 15377
PubChem 22247451
1ef7A Unbound Unbound Unbound
1ef7B Unbound Unbound Unbound

Reference for Active-site residues
resource references E.C.

Active-site residues
PDB Catalytic residues Cofactor-binding residues Modified residues Main-chain involved in catalysis Comment
1ef7A GLN 22;CYS 31;HIS 180;ASN 200 CYS 31
1ef7B GLN 22;CYS 31;HIS 180;ASN 200 CYS 31

References for Catalytic Mechanism
References Sections No. of steps in catalysis

Medline ID
PubMed ID 9738465
Journal FEBS Lett
Year 1998
Volume 434
Pages 135-9
Authors Nagler DK, Menard R
Title Human cathepsin X: a novel cysteine protease of the papain family with a very short proregion and unique insertions.
Related PDB
Related UniProtKB
Medline ID
PubMed ID 10656802
Journal J Mol Biol
Year 2000
Volume 295
Pages 939-51
Authors Sivaraman J, Nagler DK, Zhang R, Menard R, Cygler M
Title Crystal structure of human procathepsin X: a cysteine protease with the proregion covalently linked to the active site cysteine.
Related PDB
Related UniProtKB
Comments X-ray crystallography (2.67 Angstroms)
Medline ID
PubMed ID 10745011
Journal Structure Fold Des
Year 2000
Volume 8
Pages 305-13
Authors Guncar G, Klemencic I, Turk B, Turk V, Karaoglanovic-Carmona A, Juliano L, Turk D
Title Crystal structure of cathepsin X: a flip-flop of the ring of His23 allows carboxy-monopeptidase and carboxy-dipeptidase activity of the protease.
Related PDB 1ef7
Related UniProtKB

This enzyme belongs to the peptidase family-C1.
Accoriding to the literature [2], the active site is consisting of Cys31, His180, Asn200 and an oxyanion hole, which precedes the catalytic Cys31. Unlike other papain-like enzymes, three residues are inserted in the oxyanion hole region, and form a mini-loop that bends away from the active site. This paper mentioned that the oxyanion hole is formed by the sidechain of Gln and the mainchain amide group of Cys31.
Cys31, which is activated by His180, can act as a nucleophile.

Created Updated
2002-07-01 2010-02-02