INTESTINAL ALKALINE-PHOSPHATASE ISOFORMS IN RABBIT-TISSUES DIFFER IN GLYCOSYLATION PATTERNS

Objectives: In patients with advanced liver cirrhosis or chronic nephr itis, an intestinal alkaline phosphatase (IAP)-like enzyme is ectopica lly expressed in the liver or kidney. In this study, we used rabbit or gans as a human pathological model, because the rabbit liver or kidney expresses an IAP-like enzyme as the predominant isozyme, unlike human s. Methods: IAP and the IAP-like enzyme were purified from rabbit inte stine and kidney, respectively, by immunoaffinity chromatography using a monoclonal antihuman IAP antibody. Some properties of the IAP and I AP-like enzyme expressed in rabbit organs are compared. Results: Some of their catalytic and physicochemical properties differed. In particu lar, the net charge, molecular mass, and hydrophobicity of IAP from ra bbit intestine was slightly different from the IAP-like enzyme from ra bbit kidney. There was a difference in the sugar chain structure betwe en the two enzymes according to the results of lectin affinity chromat ography, and part of the peptide maps differed slightly. However, ther e was no difference in the peptide maps after treatment with endo-N-ac etylglucosaminidase F. Conclusions: The primary structures of IAP and the IAP-like enzyme are basically similar, except for the glycosylatio n process of the respective AP isozymes.