Glycosidic specificity of fucosyltransferases present in rat epididymal spermatozoa

We have recently demonstrated multiple fucosyttrans‐ferase (FT) activity In rat spermatogenic cells. To complement these findings, here we Identify and partially characterize the glycosidic linkage specificity of FTs present in spermatozoa from caput and cauda epididymides. Analysis of the acceptor substrate specificity of the FTs by thin‐layer chromatography indicated that both caput and cauda sperm expressed α(1–2)‐, α(1–3)‐, α(1–4)‐FTs as demonstrated by fucose Incorporation into phenyl‐β‐D‐galactoside, 2′‐fucosyllactose, and lacto‐N‐fucopentaose‐l, respectively. Spermatozoa from the cauda epididymidis exhibited significant decreases in the levels of α(1–2)‐, α(1–3)‐, α(1–4)‐FTs, and of total soluble FTs in comparison to spermatozoa from the caput epididymidis. The relative ratio of α(1–3)‐FT to total FT activity appeared to be significantly higher than those of α(1–2)‐ or α(1–4)‐FTs, in spermatozoa both from caput and cauda epididymides. Using different types of low molecular weight acceptors and the selective inhibition of the FT by N‐ ethyl‐maleimide, we have demonstrated that at least α(1–2)‐FT is different from α(1–3)‐ or α(1–4)‐FTs. Kinetic studies also showed that α(1–2)‐FT is different from α(1–3)‐ or α(1–4)‐FTs as demonstrated by apparent Km and Vmax values. Moreover, α(1–3)‐and α(1–4)‐FT activities in cauda sperm were found to be highly sensitive to Mn2+ but showed differential responses to divalent cations. In contrast, both α(1–3)‐ and α(1–4)‐FTs seemed to be relatively less sensitive to Mg2+. Thus, these results not only demonstrate the presence of multiple FTs in rat epididymal sperm but also differentiate Individual FTs with regard to their kinetic properties and sensitivity to both inhibitor and divalent cations.