"Adult Only" Esterase/Phospholipase A of the Small-Intestine Brush Border Membrane: Isolation, Identification of the Catalytic Site, and Biosynthesis

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• 作者：Hans Wacker ; Patrick Keller ; Anna-Karin von Balthazar ; and Giorgio Semenza
• 刊名：Biochemistry
• 出版年：1997
• 出版时间：March 18, 1997
• 年：1997
• 卷：36
• 期：11
• 页码：3336 - 3344
• 全文大小：252K
• 年卷期：v.36,no.11(March 18, 1997)
• ISSN：1520-4995

文摘

We have isolated and investigated anesterase/phospholipase A (EC 3.1.1) which is an intrinsicprotein of the small-intestine brush border membrane of adult but notof preweaning rabbits. This enzymehad been referred to previously as AdRabB [Boll, W., Schmid-Chanda,T., Semenza, G., & Mantei, N.(1993) J. Biol. Chem. 268,12901-12911]. Its amino acid sequence shows four extensive,homologousrepeats between the signal sequence and a hydrophobic stretch in theC-terminal region. We have identifieda serine residue (Ser⁴⁰⁰) in the (unexpectedly)single catalytic site and indicate that this esterase islikelyto operate by way of a Ser-His-Asp/Glu triad. Thisesterase/phospholipase A is synthesized as a singlepolypeptide chain of 170-180 kDa, agreeing well with the size deducedfrom its cognate cDNA sequence[Boll, W., et al. (1993) J. Biol. Chem. 268,12901-12911], and it undergoes (at least)N-glycosylation.Once it has reached the brush border membrane, it is subjected invivo to two types of proteolytic processing,presumably by pancreatic protease(s): a split afterArg²⁶³, with loss of the first N-terminal repeat,andtwo or more cleavages much farther downstream but still located in theluminal bulk of the protein; thesesplits lead to multiple bands of approximately 140, 125, 100, and 90kDa.