Action and cooperation in alginate degradation by three enzymes from the human gut bacterium Bacteroides eggerthii DSM 20697

作者：Mette E. Rønne, Christian Dybdahl Andersen, David Tezé, Agnes Beenfeldt Petersen, Folmer Fredslund, Emil G. P. Stender, Evan Kirk Chaberski, Jesper Holck, Finn L. Aachmann, Ditte Hededam Welner, Birte Svensson · 发表于：Journal of Biological Chemistry · 年份：2024 · DOI：10.1016/j.jbc.2024.107596 · 被引用次数：15 · 研究领域：Microbial Metabolites in Food Biotechnology、Probiotics and Fermented Foods、Enzyme Production and Characterization

Alginate is a polysaccharide consumed by humans in edible seaweed and different foods where it is applied as a texturizing hydrocolloid or in encapsulations of drugs and probiotics. While gut bacteria are found to utilize and ferment alginate to health-beneficial short-chain fatty acids, knowledge on the details of the molecular reactions is sparse. Alginates are composed of mannuronic acid (M) and its C-5 epimer guluronic acid (G). An alginate-related polysaccharide utilization locus (PUL) has been identified in the gut bacterium Bacteroides eggerthii DSM 20697. The PUL encodes two polysaccharide lyases (PLs) from the PL6 ( Be PL6) and PL17 ( Be PL17) families as well as a KdgF-like metalloprotein ( Be KdgF) known to catalyze ring-opening of 4,5-unsaturated monouronates yielding 4-deoxy-l- erythro -5-hexoseulose uronate (DEH). B. eggerthii DSM 20697 does not grow on alginate, but readily proliferates with a lag phase of a few hours in the presence of an endo -acting alginate lyase A1-I from the marine bacterium Sphingomonas sp. A1. The B. eggerthii lyases are both exo -acting and while Be PL6 is strictly G-block specific, Be PL17 prefers M-blocks. Be KdgF retained 10−27% activity in the presence of 0.1−1 mM EDTA. X-ray crystallography was used to investigate the three-dimensional structure of Be KdgF, based on which a catalytic mechanism was proposed to involve Asp102, acting as acid/base having p K a of 5.9 as determined by NMR pH titration. Be PL6 and Be PL17 cooperate in ...