Crystal structure of Aspergillus niger ATCC9642 isopullulanase
نویسندگان
چکیده
Introduction Enzymes hydrolyze pullulan are useful in the production of various oligosaccharides. Isopullulanase (IPU) from Aspergillus niger ATCC9642 was originally reported to be an enzyme which hydrolyzes specific sites of pullulan to produce isopanose (Glc-α-(1→4)-Glc-α(1→6)-Glc). Although IPU does not hydrolyze starch, the enzyme hydrolyzes substrates containing panose (Glc-α(1→6)-Glc-α-(1→4)-Glc) motif, which is also found in the structure of starch. Due to the unique properties, IPU has been assigned its own EC number (EC 3.2.1.57). Except for IPU, pullulan-hydrolyzing enzymes, such as pullulanases, Thermoactinomyces vulgaris α-amylases, and neopullulanases, are classified into glycosyl hydrolase family (GH) 13, known as the α-amylase family. In contrast, IPU is the sole enzyme which is classified into GH 49 among these pullulan-hydrolases, and no homology between IPU and α-amylase family enzymes has been found. Interestingly, IPU does not hydrolyze dextran at all, while all other GH 49 enzymes are dextran-hydrolyzing enzymes, such as endodextranase and isomaltotrio-dextranase. In this report, we describe the crystal structure of IPU.
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