The University of Queensland, Brisbane 4072 Australia.
Enzyme Microb Technol. 2012 Jan 5;50(1):57-64. doi: 10.1016/j.enzmictec.2011.09.011. Epub 2011 Oct 5.
Sucrose isomerase (SI) activity is used industrially for the conversion of sucrose into isomers, particularly isomaltulose or trehalulose, which have properties advantageous over sucrose for some food uses. All of the known microbial SIs are TIM barrel proteins that convert sucrose without need for any cofactors, with varying kinetics and product specificities. The current analysis was undertaken to bridge key gaps between the information in patents and scientific publications about the microbes and enzymes useful for sucrose isomer production. This analysis shows that microbial SIs can be considered in 5 structural classes with corresponding functional distinctions that broadly align with the taxonomic differences between producing organisms. The most widely used bacterial strain for industrial production of isomaltulose, widely referred to as "Protaminobacter rubrum" CBS 574.77, is identified as Serratia plymuthica. The strain producing the most structurally divergent SI, with a high product specificity for trehalulose, widely referred to as "Pseudomonas mesoacidophila" MX-45, is identified as Rhizobium sp. Each tested SI-producer is shown to have a single SI gene and enzyme, so the properties reported previously for the isolated proteins can reasonably be associated with the products of the genes subsequently cloned from the same isolates and SI classes. Some natural isolates with potent SI activity do not catabolize the isomer under usual production conditions. The results indicate that their industrial potential may be further enhanced by selection for variants that do not catabolize the sucrose substrate.
蔗糖异构酶（SI）活性在工业上用于将蔗糖转化为异构体，特别是异麦芽酮糖或海藻糖，它们在某些食品用途中具有优于蔗糖的特性。所有已知的微生物 SI 都是 TIM 桶蛋白，它们在不需要任何辅助因子的情况下转化蔗糖，具有不同的动力学和产物特异性。目前的分析旨在弥合专利和科学出版物中有关微生物和用于蔗糖异构化生产的酶的信息之间的关键差距。该分析表明，微生物 SI 可以分为 5 个结构类别，具有相应的功能区别，这些区别与产生生物之间的分类学差异大致一致。工业生产异麦芽酮糖最广泛使用的细菌菌株，通常称为“Protaminobacter rubrum”CBS 574.77，被鉴定为 S. plymuthica。产生结构差异最大的 SI、对海藻糖具有高产物特异性的菌株，通常称为“Pseudomonas mesoacidophila”MX-45，被鉴定为 Rhizobium sp。每个经过测试的 SI 产生菌都被证明只有一个 SI 基因和酶，因此以前报道的分离蛋白的特性可以合理地与从相同分离物和 SI 类克隆的基因的产物相关联。一些具有强 SI 活性的天然分离物在通常的生产条件下不分解异构体。结果表明，通过选择不分解蔗糖底物的变体，可以进一步提高它们的工业潜力。
