مرکز منطقه ای اطلاع رساني علوم و فناوري - Structural Modelling and Structure‐Function Analysis of Zymomonas mobilis Levansucrase

Abstract :

Levansucrases are bacterial enzymes which produce fructan polymersfrom sucrose via hydrolysis and transfructosylation activities. These polymers;levan and fructooligosaccharides are valuable for food and pharmaceuticalindustries. Levansucrases from Gram‐positive bacteria such as Bacillus subtilistend to produce levan, while those from Gram‐negative bacteria preferentiallyproduce fructooligosaccharides. Zymomonas mobilis is an efficient levansucraseproducer and its extracellular levansucrase can produce bothfructooligosaccharides and levan depending on the reaction parameters. In thisstudy, the structure of Z. mobilis levansucrase was modeled in order to help tounderstand the structure‐function relationship of the enzyme. Furthermore, aminoacids previously reported to be important for levansucrase activity were mappedon the model. The structural model presents a five‐bladed propeller with a deep,negatively charged central pocket, similar to other bacterial levansucrases.Mapping showed that amino acids which previously reported to affect fructanlength are located on the periphery of the structure covering the active site centralpocket. Thus it is showed that, for the first time, that hydrolysis andtransfructosylation reactions are catalyzed on different parts of Z. mobilislevansucrase structure. The structural location of the critical amino acids will pavethe way to identify other residues which control fructan length by site directedmutagenesis without altering the overall fold of the enzyme.