High level of α1-acid glycoprotein in human seminal plasma is associated with high branching and expression of Lewisa groups on its glycans: Supporting evidence for a prostatic origin

BACKGROUND Changes in concentration of seminal plasma α1-acid glycoprotein (AGP) have been studied in detail before. However, the source of high levels of AGP as well as the glycosylation of seminal plasma AGP has not been elucidated yet. METHODS The glycosylation of AGP was studied by crossed affinity immunoelectrophoresis using fucose-specific lectins and immunostaining. Glycan structure and monosaccharide analyses were performed by high pH anion exchange chromatography with pulsed amperometric detection. Fucosyltransferases were analyzed for activity and their substrate specificity was determined. RESULTS Two types of fucosylation were detected; Lewisx and Lewisa. Lewisa groups were only present on AGP of individuals with a high concentration and were completely absent when the AGP concentration in seminal plasma was low. Lewisa expression coincides with a higher degree of branching of the glycans and a relative increased α4-fucosyltransferase activity. The molecular weight of all seminal plasma AGP was slightly higher than of blood plasma AGP (approx. 47 vs. 41–43 kDa). CONCLUSIONS The results indicate that AGP in seminal fluid most likely originates from the prostate and that it is either α3- or α4-fucosylated. Prostate 52: 34–42, 2002. © 2002 Wiley-Liss, Inc.