| Co-Investigator(Kenkyū-buntansha) |
KOYAMA Iwao Saitama Medical School, Junior college, Associate Professor, 短期大学・臨床検査学科, 助教授 (30153688)
SAKAGISHI Yoshikatsu Saitama Medical School, School of Medicine, Full Professor, 医学部, 教授 (90049768)
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| Research Abstract |
It has been revealed that the C-terrminal amino acids of Alkaline phosphatase (ALP) molecules, except for the intestinal ALP, link to glycanphosphoinositol (GPI) involving ethanolamine and 1, 2-diacylglycerol of the GPI inserts to the biomembrane. In this regard, human placental ALP is released from the plasma membrane by phosphatidylinositol-specific phospholipase C (PIPLC), while the rat intestinal ALP is not released by this treatment (seetharam, B. ET AL. : arch. biochem. biophys., 253 : 189-l98, 1987). The fact suggests that the manner in which the GPI anchors with these ALPS is different.
With the streptozotocin-induced diabetic rats, the major ALP detected in serum was intestinal ALP. In vitro, ALP was readily released from the duodenum by piplc, but little if any was released from the ileum. The characteristics of serum ALP in rats is similar to the ileal ALP, suggesting that the circulating ALP is derived from the ileum. As reported with the IGG receptor, therefore the intestinal ALP from rats exist in both peptide-anchored and GPI-anchored forms. Other possibility, the 11eal enzyme may bears the acylated form, as human cholineesterase.
On the other hand, rabbit kidney have predominantly intestinal ALP, unlike humans. The intestinal ALP in rabbit kidney was clearly released by PIPLC treatment, like the duodenal ALP in rats. Chemical Analyses revealed that the purified intestinal ALP contains palmitate, stearate, and inositol. Molar ratios of three components were calculated to be 1 MOL, respectively. The stearate content of intestinal ALP from methylnitrosourea-induced cancer tissues of rats was calculated to be 2 MOL, the intestinal ALP in the cancer tissues was resistant to PIPLC treatment, indicating that modification of the GPI moiety in intestinal ALP molecules may alter the susceptibility to PIPLC.
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