Mas E, Crotte C, Lecestre D, Michalski J C, Escribano M J, Lombardo D, Sadoulet M O
INSERM-U. 260, Unité de Recherche de Physiopathologie des Régulations Hormono-Nutritionnelles, Faculté de Médecine, Marseille, France.
Glycobiology. 1997 Sep;7(6):745-52. doi: 10.1093/glycob/7.6.745.
The fetoacinar pancreatic protein (FAP), characterized by the mAb J28, is an oncofetal form of bile salt dependent lipase (BSDL), the expression of which is related to pancreatic differentiation and neoplastic processes. Because the J28 epitope, recognized by mAb J28, is suggested to be dependent upon carbohydrates, we have attempted to gain information about the structure of this epitope. Indeed, treatment of FAP with sodium periodate abolished the reactivity of the protein to mAb J28, which demonstrates the implication of oligosaccharides in the structure of the J28 epitope. FAP offers both O-linked and N-linked carbohydrate structures, of which, as we have determined, one is involved. Peptides obtained after cyanogen bromide cleavage were desialylated then separated by affinity chromatography on an immobilized peanut agglutinin agarose column. The peptide retained on this column carried out the reactivity with the mAb J28. Although some differences in amino acid analysis were observed, the N-terminal sequence of this peptide correlates with that of the C-terminal part of the enzyme. Carbohydrate analysis of the peptide bearing the J28 epitope revealed fucose, galactose, N-acetylgalactosamine, N-acetylglucosamine, and N-acetylneuraminic acid. The competition observed between mAb J28 and Ulex europaeus I lectin for binding to the J28 epitope suggested that fucose residue alpha (1-2) linked to a galactose residue was implicated in the structure of the J28 epitope. Alternatively, the loss of the mAb J28 reactivity upon treatment of FAP either with bovine kidney or bovine epididymis fucosidase was observed indicating that fucose residues linked at the alpha (1-2) and alpha (1-6) positions may be involved in the establishment of the structure of the J28 epitope. These observations suggest that mAb J28 recognized a particular fucosylated O-linked oligosaccharide structure located at the mucin-like extended C-terminal part of FAP.
由单克隆抗体J28所识别的胎儿胰腺蛋白（FAP）是一种癌胚形式的胆汁盐依赖性脂肪酶（BSDL），其表达与胰腺分化和肿瘤形成过程相关。由于单克隆抗体J28所识别的J28表位被认为依赖于碳水化合物，我们试图获取有关该表位结构的信息。事实上，用高碘酸钠处理FAP可消除该蛋白与单克隆抗体J28的反应性，这表明寡糖参与了J28表位的结构。FAP具有O-连接和N-连接的碳水化合物结构，正如我们所确定的，其中一种参与其中。溴化氰裂解后得到的肽经去唾液酸化处理，然后在固定化花生凝集素琼脂糖柱上通过亲和色谱法分离。保留在该柱上的肽与单克隆抗体J28发生反应。尽管在氨基酸分析中观察到一些差异，但该肽的N端序列与该酶C端部分的序列相关。对带有J28表位的肽进行碳水化合物分析，发现含有岩藻糖、半乳糖、N-乙酰半乳糖胺、N-乙酰葡糖胺和N-乙酰神经氨酸。单克隆抗体J28与欧洲荆豆I凝集素之间在结合J28表位上的竞争表明，与半乳糖残基相连的α（1-2）岩藻糖残基参与了J28表位的结构。另外，在用牛肾或牛附睾岩藻糖苷酶处理FAP后，观察到单克隆抗体J28反应性的丧失，这表明连接在α（1-2）和α（1-6）位置的岩藻糖残基可能参与了J28表位结构的形成。这些观察结果表明，单克隆抗体J28识别位于FAP粘蛋白样延伸C端部分的一种特定的岩藻糖基化O-连接寡糖结构。
