5wqs | pdb_00005wqs

Crystal structure of Apo Beta-Amylase from Sweet potato

spinqualitylabelsall models 5wqs, resolution 1.90Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 5wqs is a 1 chain structure with sequence from Ipomoea batatas. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Ligands: IPA Related: 5wqu Activity: Beta-amylase, with EC number 3.2.1.2 Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Publication Abstract from PubMed The conversion of starch to maltose is catalysed in plants by beta-amylase. The enzymatic mechanism has been well-characterized for the soybean and barley enzymes, which utilise a glutamic acid-glutamate pair. In the present study, we present a surprise observation of maltotetraose at the active site, the presence of which elucidates the clear role of Thr344 as a conformational "switch" between substrate binding and product release during hydrolysis. This observation is confirmed by the selection of maltotetraose by the crystallized enzyme although that carbohydrate was present in only trace amounts. The conformation of the residues in the substrate-binding site changed upon substrate binding, leading to the movement of threonine, glutamic acid, and the loop conformation, elucidating a missing link in the existing mechanism. By aligning our substrate-free and maltotetraose-bound structures with other existing structures, the sequence of events from substrate binding to hydrolysis can be visualized. Apart from this, the evolutionary relationship among beta-amylases of bacterial and amyloplastic origin could be established. The presence of a sugar-binding domain in the bacterial enzyme and its absence in the plant counterpart could be attributed to a carbohydrate-rich environment. Interestingly, cladogram analysis indicates the presence of N-terminal additions in some plant beta-amylases. Based on sequence similarity, we postulate that the role of such additions is important for the regulation of enzymatic activity, particularly under stress conditions. Structural insights on starch hydrolysis by plant beta-amylase and its evolutionary relationship with bacterial enzymes.,Vajravijayan S, Pletnev S, Mani N, Pletneva N, Nandhagopal N, Gunasekaran K Int J Biol Macromol. 2018 Jul 1;113:329-337. doi: 10.1016/j.ijbiomac.2018.02.138., Epub 2018 Feb 23. PMID:29481953 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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