Structure and mechanism of sulfofructose transaldolase, a key enzyme in sulfoquinovose metabolism.
Structure and mechanism of sulfofructose transaldolase, a key enzyme in sulfoquinovose metabolism.
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DOI：
10.1016/j.str.2023.01.010
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发表时间：
2023-02
期刊：
影响因子：
5.7
通讯作者：
A. Snow;Mahima Sharma;Palika Abayakoon;Spencer J. Williams;J. N. Blaza;G. Davies
中科院分区：
文献类型：
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作者：
A. Snow;Mahima Sharma;Palika Abayakoon;Spencer J. Williams;J. N. Blaza;G. Davies
磺基喹诺糖（SQ）是植物硫脂（磺基喹诺糖基二酰基甘油）的重要组成部分，也是生物硫的主要环境储存库。SQ的分解是由细菌通过磺基糖酵解途径实现的。磺基糖酵解磺基果糖转醛醇酶（磺基-SFT）途径被肠道寄居的厚壁菌和土壤腐殖菌使用。在SQ异构化为磺基果糖（SF）后，同名酶催化SF将二羟基丙酮转移到3C/4C受体的transaldol反应，以产生磺基乙醛和果糖-6-磷酸或景天庚酮糖-7-磷酸。我们报道了巨大芽孢杆菌SF转醛醇酶的载脂蛋白和配体结合形式的三维冷冻电镜结构，揭示了由两个五聚体环形成的十聚体结构。我们证明了一个共价的“席夫碱”的中间体形成的反应SF与赖氨酸89内的保守的Asp-Lys-Glu催化三联体和定义的Arg-Trp-Arg磺酸识别三联体。磺基-SFT途径的特征酶的结构表征提供了磺基糖的磺酸基的分子识别的关键见解。
Sulfoquinovose (SQ) is a key component of plant sulfolipids (sulfoquinovosyl diacylglycerols) and a major environmental reservoir of biological sulfur. Breakdown of SQ is achieved by bacteria through the pathways of sulfoglycolysis. The sulfoglycolytic sulfofructose transaldolase (sulfo-SFT) pathway is used by gut-resident firmicutes and soil saprophytes. After isomerization of SQ to sulfofructose (SF), the namesake enzyme catalyzes the transaldol reaction of SF transferring dihydroxyacetone to 3C/4C acceptors to give sulfolactaldehyde and fructose-6-phosphate or sedoheptulose-7-phosphate. We report the 3D cryo-EM structure of SF transaldolase fromBacillus megateriumin apo and ligand bound forms, revealing a decameric structure formed from two pentameric rings of the protomer. We demonstrate a covalent "Schiff base" intermediate formed by reaction of SF with Lys89 within a conserved Asp-Lys-Glu catalytic triad and defined by an Arg-Trp-Arg sulfonate recognition triad. The structural characterization of the signature enzyme of the sulfo-SFT pathway provides key insights into molecular recognition of the sulfonate group of sulfosugars.