Human cathepsin X: a novel cysteine protease of the papain family with a very short proregion and unique insertions

FEBS Lett. 1998 Aug 28;434(1-2):135-9. doi: 10.1016/s0014-5793(98)00964-8.


A novel cDNA encoding a cysteine protease of the papain family named cathepsin X was obtained by PCR amplification from a human ovary cDNA library. The cathepsin X cDNA is ubiquitously expressed in human tissues and contains an open reading frame of 912 nucleotides encoding a predicted protein of 303 amino acids. All highly conserved regions in papain-like cysteine proteases including the catalytic residues are present in cathepsin X. The mature part of cathepsin X is 26-32% identical to human cathepsins B, C, H, K, L, O, S and W. The cathepsin X sequence contains several unique features: (i) a very short proregion; (ii) a three amino acid residue insertion in a highly conserved region between the glutamine of the putative oxyanion hole and the active site cysteine; and (iii) a second insertion of 15 amino acid residues that can be aligned with the occluding loop region in cathepsin B.

MeSH terms

  • Amino Acid Sequence
  • Base Sequence
  • Cathepsin K
  • Cathepsins / genetics*
  • Cathepsins / metabolism*
  • Cysteine Endopeptidases / genetics*
  • Cysteine Endopeptidases / metabolism
  • DNA Transposable Elements
  • Humans
  • Molecular Sequence Data
  • Papain / genetics*
  • Sequence Alignment
  • Sequence Analysis


  • DNA Transposable Elements
  • Cathepsins
  • Cysteine Endopeptidases
  • Papain
  • CTSK protein, human
  • Cathepsin K

Associated data

  • GENBANK/AF073890