title: O-acetylation and de-O-acetylation of sialic acids in human colorectal carcinoma.
abstract: A decrease in the level of O-acetylated sialic acids observed in colorectal carcinoma may lead to an increase in the expression of sialyl Lewis(X), a tumor-associated antigen, which is related to progression of colorectal cancer to metastasis. The underlying mechanism for this reduction is, however, not fully understood. Two enzymes are thought to be primarily responsible for the turnover of O-acetyl ester groups on sialic acids; sialate-O-acetyltransferase (OAT) and sialate-O-acetylesterase (OAE). We have previously reported the characterization of OAT activity from normal colon mucosa, which efficiently O-acetylates CMP-Neu5Ac exclusively in the Golgi apparatus prior to the action of sialyltransferase. In this report we describe the identification of a lysosomal and a cytosolic OAE activity in human colonic mucosa that specifically hydrolyses 9-O-acetyl groups on sialic acid. Utilizing matched resection margin and cancer tissue from colorectal carcinoma patients we provide strong evidence suggesting that the level of O-acetylated sialic acids present in normal and diseased human colon may be dependent on the relative activities of OAT to lysosomal OAE. Furthermore, we show that the level of free cytosolic Neu5,9Ac2 in human colon is regulated by the relative activity of the cytosolic OAE.
authors.affiliation: Biochemisches Institut, Christian-Albrechts-Universität zu Kiel, Germany.
authors.forename: Yanqin
authors.initials: Y
authors.lastname: Shen
authors.forename: Guido
authors.initials: G
authors.lastname: Kohla
authors.forename: Aicha L
authors.initials: AL
authors.lastname: Lrhorfi
authors.forename: Bence
authors.initials: B
authors.lastname: Sipos
authors.forename: Holger
authors.initials: H
authors.lastname: Kalthoff
authors.forename: Gerrit J
authors.initials: GJ
authors.lastname: Gerwig
authors.forename: Johannis P
authors.initials: JP
authors.lastname: Kamerling
authors.forename: Roland
authors.initials: R
authors.lastname: Schauer
authors.forename: Joe
authors.initials: J
authors.lastname: Tiralongo
mesh_terms: D000107:Acetylation; D000115:Acetylesterase; D000123:Acetyltransferases / Q000378:metabolism*; D002265:Carboxylic Ester Hydrolases / Q000378:metabolism*; D016022:Case-Control Studies; D002851:Chromatography, High Pressure Liquid; D003106:Colon / Q000201:enzymology; D015179:Colorectal Neoplasms / Q000201:enzymology*; D003600:Cytosol / Q000201:enzymology; D008401:Gas Chromatography-Mass Spectrometry; D006801:Humans; D008247:Lysosomes / Q000201:enzymology; D019158:N-Acetylneuraminic Acid / Q000378:metabolism*; D012794:Sialic Acids / Q000378:metabolism*
chemical_list: D012794:Sialic Acids; D000123:Acetyltransferases; C018766:N-acylneuraminate-9(7)-O-acetyltransferase; D002265:Carboxylic Ester Hydrolases; D000115:Acetylesterase; C046298:sialate O-acetylesterase; D019158:N-Acetylneuraminic Acid