Isolation and characterization of human cathepsin V: a major proteinase in corneal epithelium

Invest Ophthalmol Vis Sci. 1998 Sep;39(10):1789-96.


Purpose: To isolate and characterize a novel cathepsin gene, as part of the systematic isolation of genes uniquely active in corneal epithelium.

Methods: For the isolation of a full-length cDNA clone, a probe was selected from a set of expressed sequence tag clones classified as unique to corneal epithelium. Inserted cDNA was introduced into insect cells using a baculovirus expression system, and the secretion of recombinant protein was identified using antisera against a synthetic peptide. Proteolytic activity was determined using bovine serum albumin (BSA) as substrate. The expressions of the novel cathepsin in human cornea and other tissues were examined by reverse transcription-polymerase chain reaction (RT-PCR).

Results: The full-length cDNA clone encoded a peptide of 334 amino acids with 82% identity with bovine cathepsin L and 77% identity with human cathepsin L when aligned. The recombinant protein produced in the baculovirus expression system cleaves BSA, and its activity was inhibited by the cysteine proteinase inhibitors E-64 and leupeptin, but not by pepstatin A, phenylmethylsulfonyl fluoride, and EDTA. By RT-PCR, a low level of expression was observed in some other epithelial tissues of ectodermal origin, but only in cornea was it higher than cathepsin L, which is known to be a general lysosomal cathepsin. Cathepsin V protein was detected in human corneal epithelium by western blot analysis, but not in tear fluid.

Conclusions: The amino acid homology and proteolytic activity of the recombinant protein indicate that the novel gene is a new member of the cathepsins that have features of cysteine proteinase. Its uniquely high expression in corneal epithelium strongly implies an important role in corneal physiology.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Baculoviridae / genetics
  • Base Sequence
  • Blotting, Western
  • Cathepsin L
  • Cathepsins / genetics
  • Cathepsins / isolation & purification*
  • Cathepsins / metabolism
  • Cysteine Endopeptidases / genetics
  • Cysteine Endopeptidases / isolation & purification*
  • Cysteine Endopeptidases / metabolism
  • Cysteine Proteinase Inhibitors / pharmacology
  • DNA Primers / chemistry
  • DNA, Complementary / analysis
  • Endopeptidases*
  • Epithelium, Corneal / chemistry*
  • Epithelium, Corneal / drug effects
  • Epithelium, Corneal / metabolism
  • Eye Proteins / genetics
  • Eye Proteins / isolation & purification*
  • Eye Proteins / metabolism
  • Gene Expression
  • Humans
  • Molecular Sequence Data
  • Polymerase Chain Reaction
  • Rabbits
  • Recombinant Proteins / metabolism
  • Sequence Homology, Amino Acid
  • Sequence Homology, Nucleic Acid
  • Tears / metabolism
  • Transcription, Genetic
  • Transfection


  • Cysteine Proteinase Inhibitors
  • DNA Primers
  • DNA, Complementary
  • Eye Proteins
  • Recombinant Proteins
  • Cathepsins
  • Endopeptidases
  • Cysteine Endopeptidases
  • CTSL protein, human
  • Cathepsin L

Associated data

  • GENBANK/AB001928