期刊
APPLIED AND ENVIRONMENTAL MICROBIOLOGY
卷 86, 期 23, 页码 -出版社
AMER SOC MICROBIOLOGY
DOI: 10.1128/AEM.01796-20
关键词
marine microbe; organic matter; carbohydrate processing; extracellular enzyme; biogeochemical cycle; catalytic mechanism; substrate specificity
资金
- Strategic Priority Research Program of the Chinese Academy of Sciences [XDA13020301]
- Guangdong Natural Science Foundation [2019A1515011629]
- Science and Technology Project of Guangzhou [201904010165]
- Key Special Project for Introduced Talents Team of Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou) [GML2019ZD0404]
- National Natural Science Foundation of China [41406193]
- Administration of Ocean and Fisheries of Guangdong Province [GD2012-D01-002]
- Platform Project for Supporting Drug Discovery and Life Science Research (Basis for Supporting Innovative Drug Discovery and Life Science Research [BINDS]) [JP19am0101071, 1430]
Laminarin is an abundant algal polysaccharide that serves as carbon storage and fuel to meet the nutrition demands of heterotrophic microbes. Laminarin depolymerization catalyzed by microbial extracellular enzymes initiates remineralization, a key process in ocean biogeochemical cycles. Here, we described a glycoside hydrolase 16 (GH16) family laminarinase from a marine alga-associated Flavobacterium at the biochemical and structural levels. We found that the endolytic enzyme cleaved laminarin with a preference for beta-1,3-glycoside linkages and showed transglycosylation activity across a broad range of acceptors. We also solved and compared high-resolution crystal structures of laminarinase in the apo form and in complex with beta-1,3-tetrasaccharides, revealing an expanded catalytic cleft formed following substrate binding. Moreover, structure and mutagenesis studies identified multiple specific contacts between the enzyme and glucosyl residues essential for the substrate specificity for beta-1,3-glucan. These results provide novel insights into the structural requirements for substrate binding and catalysis of GH16 family laminarinase, enriching our understanding of bacterial utilization of algal laminarin. IMPORTANCE Heterotrophic bacterial communities are key players in marine biogeochemical cycling due to their ability to remineralize organic carbon. Processing of complex organic matter requires heterotrophic bacteria to produce extracellular enzymes with precise specificity to depolymerize substrates to sizes sufficiently small for uptake. Thus, extracellular enzymatic hydrolysis initiates microbe-driven heterotrophic carbon cycling. In this study, based on biochemical and structural analyses, we revealed the depolymerization mechanism of beta-1,3-glucan, a carbon reserve in algae, by laminarinase from an alga-associated marine Flavobacterium. The findings provide new insights into the substrate recognition and catalysis of bacterial laminarinase and promote a better understanding of how extracellular enzymes are involved in organic matter cycling.
作者
我是这篇论文的作者
点击您的名字以认领此论文并将其添加到您的个人资料中。
推荐
暂无数据