The A33 antigen is a cell surface glycoprotein expressed in human gastrointestinal epithelium and in 95% of colorectal cancers. We have compared the N-linked glycosylation profile of A33 antigen naturally expressed in a human colorectal. cancer cell line with recombinant human A33 antigen (rA33) produced in insect cell culture using the baculovirus expression vector. N-Linked glycans were enzymatically released from the protein, and glycan composition was analyzed by HPLC. In three insect cell lines tested (Sf-21, Tn5B1-4, and Tn-4s), glycosylation of rA33 was dominated by high mannose structures (M(5)Gn(2) to M(9)Gn(2); 78-95% of total N-linked glycans), with M(8)Gn(2) being the single most abundant glycoform. A33 antigen naturally expressed in the SW1222 human colon cancer cell line (A33) also possessed a high abundance of high mannose glycans (72%). No complex glycosylation was detected on rA33 expressed in insect cells. Natural A33 was galactosylated to a small extent (6%). These results illustrate a case of similar glycosylation of a glycoprotein between a recombinant version produced in insect cell culture and its counterpart naturally expressed in human cell culture.