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ζ‐Crystallin catalyzes the reductive activation of 2,4,6‐trinitrotoluene to generate reactive oxygen species: a proposed mechanism for the induction of cataracts
Author(s) -
Kumagai Yoshito,
Wakayama Toshihiko,
Li Song,
Shinohara Azusa,
Iwamatsu Akihiro,
Sun Guifan,
Shimojo Nobuhiro
Publication year - 2000
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/s0014-5793(00)01841-x
Subject(s) - superoxide , chemistry , reactive oxygen species , superoxide dismutase , biochemistry , enzyme , oxidative stress , antioxidant
Exposure to 2,4,6‐trinitrotoluene (TNT) has been shown to cause induction of cataract in which oxidative stress plays a critical role. From bovine lens we purified to homogeneity and identified an enzyme that catalyzes the reduction of TNT, resulting in the production of reactive oxygen species. The final preparation of TNT reductase showed a single band with a subunit molecular weight of 38 kDa on SDS–PAGE. Sequence data from peptides obtained by digestion with lysylendopeptidase Achromobacter protease I (API) revealed that TNT reductase is identical to ζ‐crystallin. Superoxide anions were formed during reduction of TNT by ζ‐crystallin, though negligible enzyme activity or protein content for superoxide dismutase, a superoxide scavenging enzyme, was found in the lens. Thus, the present results suggest that the induction of cataracts by TNT may be associated with increased oxidative stress, as a result of reductive activation of TNT generating superoxide anions, there being minimal antioxidant enzyme activity for defense against reactive oxygen species exogenously produced in the lens.