We have reported the presence of a new sulfhydryl oxidizing enzyme in the male reproductive tract. The enzyme, a sulfhydryl oxidase, catalyzes the reaction 2R-SH plus O2 yields R-S-S-R plus H2O2. The localization of the enzyme within the reproductive tract and its reactivity towards sulfhydryl compounds suggest that the enzyme may play a role in controlling the sulfhydryl chemistry of the tract. In these studies we propose to purify the enzyme from hamster epididymal fluid by a variety of fractionation procedures including ammonium sulfate fractionation, Sephadex gel filtration, ion exchange chromatography on Bio-Gel A and hydroxyapatite, and affinity chromatography on Thiol-Sepharose gel. The purified enzyme will then be characterized with respect to its pH and temperature optima, cofactor requirement, substrate specificity, and sensitivity to various inhibitors and to changes in ionic strength. In addition to these biochemical investigations, physiological studies will be performed to determine whether the site of synthesis of the enzyme in epididymal fluid is the epididymis itself, or the testis. Experiments will also be performed to determine if the maintenance of enzyme levels within the epididymis is androgen dependent. Epididymal maturation of spermatozoa involves, in part, the formation of structurally vital disulfide bonds within the sperm nuclei and tails. In vitro studies suggest that the integrity of these sperm disulfide bonds may be influenced by the sulfhydryl chemistry of the reproductive tract. The proposed studies will increase our understanding of the sulfhydryl chemistry of the tract and the factors which may control it.