Tyrosine cross-linking of extracellular matrix is catalyzed by Duox, a multidomain oxidase/peroxidase with homology to the phagocyte oxidase subunit gp91 phox
Wa. Edens et al., Tyrosine cross-linking of extracellular matrix is catalyzed by Duox, a multidomain oxidase/peroxidase with homology to the phagocyte oxidase subunit gp91 phox, J CELL BIOL, 154(4), 2001, pp. 879-891
High molecular weight homologues of gp91 phox, the superoxide-generating su
bunit of phagocyte nicotinamide adenine dinucleotide phosphate (NADPH)-oxid
ase, have been identified in human (h) and Caenorhahditis elegans (Ce), and
are termed Duox for "dual oxidase" because they have both a peroxidase hom
ology domain and a gp91 phox domain. A topology model predicts that the enz
yme will utilize cytosolic NADPH to generate reactive oxygen, but the funct
ion of the ecto peroxidase domain was unknown. Ce-Duox1 is expressed in hyp
odermal cells underlying the cuticle of larval animals. To investigate func
tion, RNA interference (RNAi) was carried out in C. elegans. RNAi animals s
howed complex phenotypes similar to those described previously in mutations
in collagen biosynthesis that are known to affect the cuticle, an extracel
lular matrix. Electron micrographs showed gross abnormalities in the cuticl
e of RNAi animals. In cuticle, collagen and other proteins are cross-linked
via di- and trityrosine linkages, and these linkages were absent in RNAi a
nimals. The expressed peroxidase domains of both Ce-Duox1 and h-Duox showed
peroxidase activity and catalyzed crosslinking of free tyrosine ethyl este
r. Thus, Ce-Duox catalyzes the cross-linking of tyrosine residues involved
in the stabilization of cuticular extracellular matrix.