Enzymatic reduction of disulfide bonds in lysosomes: characterization of a gamma-interferon-inducible lysosomal thiol reductase (GILT)

Proc Natl Acad Sci U S A. 2000 Jan 18;97(2):745-50. doi: 10.1073/pnas.97.2.745.


Proteins internalized into the endocytic pathway are usually degraded. Efficient proteolysis requires denaturation, induced by acidic conditions within lysosomes, and reduction of inter- and intrachain disulfide bonds. Cytosolic reduction is mediated enzymatically by thioredoxin, but the mechanism of lysosomal reduction is unknown. We describe here a lysosomal thiol reductase optimally active at low pH and capable of catalyzing disulfide bond reduction both in vivo and in vitro. The active site, determined by mutagenesis, consists of a pair of cysteine residues separated by two amino acids, similar to other enzymes of the thioredoxin family. The enzyme is a soluble glycoprotein that is synthesized as a precursor. After delivery into the endosomal/lysosomal system by the mannose 6-phosphate receptor, N- and C-terminal prosequences are removed. The enzyme is expressed constitutively in antigen-presenting cells and induced by IFN-gamma in other cell types, suggesting a potentially important role in antigen processing.

Publication types

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

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Base Sequence
  • Binding Sites / genetics
  • COS Cells
  • DNA, Complementary / chemistry
  • DNA, Complementary / genetics
  • Disulfides / metabolism*
  • Endosomes / enzymology
  • Endosomes / ultrastructure
  • Enzyme Induction / drug effects
  • Humans
  • Hydrogen-Ion Concentration
  • Interferon-gamma / pharmacology
  • Lysosomes / enzymology*
  • Mannosephosphates / metabolism
  • Microscopy, Immunoelectron
  • Molecular Sequence Data
  • Mutagenesis
  • Oxidation-Reduction
  • Protein Disulfide Reductase (Glutathione) / biosynthesis
  • Protein Disulfide Reductase (Glutathione) / genetics
  • Protein Disulfide Reductase (Glutathione) / metabolism
  • Protein Processing, Post-Translational
  • Sequence Analysis, DNA
  • Tumor Cells, Cultured / drug effects
  • Tumor Cells, Cultured / enzymology
  • Tumor Cells, Cultured / ultrastructure


  • DNA, Complementary
  • Disulfides
  • Mannosephosphates
  • mannose-6-phosphate
  • Interferon-gamma
  • Protein Disulfide Reductase (Glutathione)

Associated data

  • GENBANK/AF097362