Structural characteristics of the N-glycans of two isoforms of prostate-specific antigens purified from human seminal fluid

Prostate-specific antigen (PSA) is a glycosylated chymotrypsin-like serine protease and is found mainly in prostatic tissue and seminal fluid. We puri fied two forms of PSA (PSA-A and PSA-B) from human seminal fluid with pI va lues of approx. 7.2 and approx. 6.9, respectively. To characterize the N-gl ycans of the two isoforms, the sugar chains were liberated by hydrazinolysi s followed by N-acetylation, and derivatized with 2-aminobenzamide. Both PS A-A and PSA-B contained mono- and disialylated sugar chains, although PSA-B had a much higher content of the latter. After removal of sialic acid resi dues by sialidase digestion, mono- and biantennary N-glycans and three oute r chain moieties (Gal beta1-4GlcNAc beta1-, GlcNAc beta1-, GalNAc beta1-4Gl cNA beta1-) were found in both samples. However, the ratios of each N-glyca n were different. These results indicate that PSA-A and PSA-B differ not on ly in their sialic acid contents, but also in their outer chain features. ( C) 2001 Elsevier Science B.V. All rights reserved.