GLYCOSIDIC SPECIFICITY OF FUCOSYL-TRANSFERASES PRESENT IN RAT EPIDIDYMAL SPERMATOZOA

We have recently demonstrated multiple fucosyltransferase (FT) activit y in rat spermatogenic cells. To complement these findings, here we id entify and partially characterize the glycosidic linkage specificity o f FTs present in spermatozoa from caput and cauda epididymides. Analys is of the acceptor substrate specificity of the FTs by thin-layer chro matography indicated that both caput and cauda sperm expressed alpha(1 -2)-, alpha(1-3)-, alpha(1-4)-FTs as demonstrated by fucose incorporat ion into phenyl-beta-D-galactoside, 2'-fucosyllactose, and lacto-N-fuc opentaose-1, respectively. Spermatozoa from the cauda epididymidis exh ibited significant decreases in the levels of alpha(1-2)-, alpha(1-3)- , alpha(1-4)-FTs, and of total soluble FTs in comparison to spermatozo a from the caput epididymidis. The relative ratio of alpha(1-3)-FT to total FT activity appeared to be significantly higher than those of al pha(1-2)- or alpha(1-4)-FTs, in spermatozoa both from caput and cauda epididymides. Using different types of low molecular weight accepters and the selective inhibition of the FT by N-ethylmaleimide, we have de monstrated that at least alpha(1-2)-FT is different from alpha(1-3)- o r alpha(1-4)-FTs. Kinetic studies also showed that alpha(1-2)-FT is di fferent from alpha(1-3)- or alpha(1-4)-FTs as demonstrated by apparent K-m and V-max values. Moreover, alpha(1-3)- and alpha(1-4)-FT activit ies in cauda sperm were found to be highly sensitive to Mn2+ but showe d differential responses to divalent cations. In contrast, both alpha( 1-3)and alpha(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 re gard to their kinetic properties and sensitivity to both inhibitor and divalent cations.