Affiliations: Department of Biological Chemistry, University of
Padova, Viale G. Colombo 3, I-35121 Padova, Italy | Department of Biochemistry, Technical University of
Braunschweig, Mascheroder Weg 1, D-38124 Braunschweig, Germany
Note: [] Department of Biological Chemistry, University of Padova, Viale
G. Colombo 3, I-35121 Padova, Italy. Tel.: +39 049 8276103; Fax: +39 049
8073310; E-mail: mmaior@civ.bio.unipd.it
Abstract: PHGPx of rat sperm mitochondrial capsule is cross-linked and
inactive. The enzyme is in part released in an active form by mercaptoethanol.
Treatment with H_2O_2 of reduced and
solubilised capsule proteins, in the absence of any added reductant, results
in: i) H_2O_2 consumption which depends
on the presence of both, PHGPx activity and protein thiols; ii) protein thiol
oxidation with a stoichiometry of 2 equivalents of thiol per mole of
hydroperoxide and, iii) PHGPx inactivation and cross-linking. SDS-PAGE analysis
of monobromobimane-labeled proteins, following incubation with
H_2O_2, shows that the oxidation takes
place in specific bands in the area of 20~kDa. It is concluded that the protein
thiol peroxidase activity of PHGPx is responsible for cross-linking proteins in
the mammalian sperm capsule and accounts for the selenium dependency of
spermatogenesis.
