{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,16]],"date-time":"2026-09-16T15:05:04Z","timestamp":1789571104371,"version":"build-2803163510"},"reference-count":36,"publisher":"Oxford University Press (OUP)","issue":"10","license":[{"start":{"date-parts":[[2026,9,8]],"date-time":"2026-09-08T00:00:00Z","timestamp":1788825600000},"content-version":"vor","delay-in-days":16,"URL":"https:\/\/creativecommons.org\/licenses\/by-nc\/4.0\/"}],"funder":[{"name":"Swiss National Foundation","award":["310030_212231"],"award-info":[{"award-number":["310030_212231"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":[],"published-print":{"date-parts":[[2026,8,23]]},"abstract":"<jats:title>Abstract<\/jats:title>\n                  <jats:p>Sialic acid on intestinal glycans is modified by O-acetylation, a modification that can protect glycans from bacterial degradation and modulate immune recognition. However, the specificity of gut bacterial sialidases toward O-acetylated sialic acid remains poorly defined. Here, we characterized six GH33 sialidases from Bacteroides spp. and Akkermansia muciniphila using chemically defined 4-methylumbelliferyl substrates bearing 4-O-, 7-O-, or 8\/9-O-acetylated N-acetylneuraminic acid (Neu5Ac). All enzymes adopted the canonical \u03b2-propeller fold and displayed distinct substrate preferences. While 8\/9-O-acetylated Neu5Ac was broadly tolerated and 7-O-acetylation variably accommodated, all commensal sialidases were unable to cleave 4-O-acetylated Neu5Ac. Endogenous murine caecal sialidase activity showed the same pattern. Removal of the 4-O-acetyl group by a viral sialate O-acetylesterase restored cleavage, demonstrating that the C4 acetyl group directly prevents hydrolysis. On primary colonic and splenic lymphocytes, the bacterial sialidases produced enzyme-, linkage-, cell-type-, and tissue-dependent changes in sialic acid-dependent lectin and Siglec-E-Fc binding. In colon tissue, however, only the broad-spectrum pathogen-derived NanI sialidase consistently reduced SNA, MAL2, and Siglec-E-Fc binding, while the commensal enzymes caused more restricted changes. These findings demonstrate pronounced position-dependent effects of Neu5Ac O-acetylation on the activity of the sialidases tested and reveal substantial enzyme-specific differences in the processing of defined O-acetylated substrates.<\/jats:p>","DOI":"10.1093\/glycob\/cwag078","type":"journal-article","created":{"date-parts":[[2026,9,7]],"date-time":"2026-09-07T11:24:17Z","timestamp":1788780257000},"source":"Crossref","is-referenced-by-count":0,"title":["Defined O-acetylated Neu5Ac substrates reveal position-specific preferences of gut bacterial sialidases"],"prefix":"10.1093","volume":"36","author":[{"given":"Nikita","family":"Podvalnyy","sequence":"first","affiliation":[{"name":"Institute of Physiology, University of Zurich , Winterthurerstrasse 190, Zurich CH-8057 ,","place":["Switzerland"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Luca","family":"Plan","sequence":"additional","affiliation":[{"name":"Institute of Physiology, University of Zurich , Winterthurerstrasse 190, Zurich CH-8057 ,","place":["Switzerland"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Sereina","family":"Gut","sequence":"additional","affiliation":[{"name":"Institute of Physiology, University of Zurich , Winterthurerstrasse 190, Zurich CH-8057 ,","place":["Switzerland"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Patricia","family":"Figueiredo-Campos","sequence":"additional","affiliation":[{"name":"Institute of Physiology, University of Zurich , Winterthurerstrasse 190, Zurich CH-8057 ,","place":["Switzerland"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Cecilia A","family":"Lai","sequence":"additional","affiliation":[{"name":"Institute of Physiology, University of Zurich , Winterthurerstrasse 190, Zurich CH-8057 ,","place":["Switzerland"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7276-737X","authenticated-orcid":false,"given":"Thierry","family":"Hennet","sequence":"additional","affiliation":[{"name":"Institute of Physiology, University of Zurich , Winterthurerstrasse 190, Zurich CH-8057 ,","place":["Switzerland"]}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"286","published-online":{"date-parts":[[2026,9,8]]},"reference":[{"issue":"3","key":"2026091610365011600_ref1","doi-asserted-by":"publisher","first-page":"231","DOI":"10.1007\/s10719-008-9183-z","article-title":"Multiple changes in sialic acid biology during human evolution","volume":"26","author":"Varki","year":"2009","journal-title":"Glycoconj J"},{"issue":"3","key":"2026091610365011600_ref2","doi-asserted-by":"publisher","first-page":"102989","DOI":"10.1016\/j.jbc.2023.102989","article-title":"Biochemical and structural basis of sialic acid utilization by gut 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