Lens transglutaminase and cataract formation

Proc Natl Acad Sci U S A. 1981 Mar;78(3):1356-60. doi: 10.1073/pnas.78.3.1356.

Abstract

A protein polymer characteristically present in human cataract was shown to contain significant amounts of gamma-glutamyl-epsilon-lysine isopeptides. It is proposed that these crosslinks are produced by the action of transglutaminase (R-glutaminyl-peptide:amine-gamma-glutamyl-yltransferase, EC 2.3.2.13), which is all the more plausible because lens contains the enzyme and endogenous protein substrates for it. The enzyme is similar to that obtained from liver and is Ca2+ dependent. Highest apparent activity is found in lens cortex. When cortex homogenate from the rabbit was incubated in the presence of Ca2+ with either [14C]putrescine or with dansylcadaverine, a a selective incorporation of the radioactive or fluorescent amine into the heavier subunits (Mr approximately 26,000 and 30,000) of beta-crystallins could be demonstrated. Possible modes of regulating the crosslinking activity of this enzyme in lens are discussed.

Publication types

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

MeSH terms

  • Animals
  • Calcium / pharmacology
  • Cataract / enzymology
  • Cataract / etiology*
  • Cattle
  • Crystallins / analysis
  • Guinea Pigs
  • Humans
  • Kinetics
  • Lens, Crystalline / enzymology*
  • Macromolecular Substances
  • Molecular Weight
  • Putrescine / metabolism
  • Rabbits
  • Rats
  • Species Specificity
  • gamma-Glutamyltransferase / metabolism*

Substances

  • Crystallins
  • Macromolecular Substances
  • gamma-Glutamyltransferase
  • Calcium
  • Putrescine