Molecular cloning and heterologous expression of the isopullulanase gene from Aspergillus niger A.T.C.C. 9642.
Isopullulanase (IPU) from Aspergillus niger A.T.C.C. (American Type Culture Collection) 9642 hydrolyses pullulan to isopanose. IPU is important for the production of isopanose and is used in the structural analysis of oligosaccharides with alpha-1,4 and alpha-1,6 glucosidic linkages. We have isolated the ipuA gene encoding IPU from the filamentous fungi A. niger A.T.C.C. 9642. The ipuA gene encodes an open reading frame of 1695 bp (564 amino acids). IPU contained a signal sequence of 19 amino acids, and the molecular mass of the mature form was calculated to be 59 kDa. IPU has no amino-acid-sequence similarity with the other pullulan-hydrolysing enzymes, which are pullulanase, neopullulanase and glucoamylase. However, IPU showed a high amino-acid-sequence similarity with dextranases from Penicillium minioluteum (61%) and Arthrobacter sp. (56%). When the ipuA gene was expressed in Aspergillus oryzae, the expressed protein (recombinant IPU) had IPU activity and was immunologically reactive with antibodies raised against native IPU. The substrate specificity, thermostability and pH profile of recombinant IPU were identical with those of the native enzyme, but recombinant IPU (90 kDa) was larger than the native enzyme (69-71 kDa). After deglycosylation with peptide-N-glycosidase F, the deglycosylated recombinant IPU had the same molecular mass as deglycosylated native enzyme (59 kDa). This result suggests that the carbohydrate chain of recombinant IPU differed from that of the native enzyme.
Aoki
H
H
Department of Applied Biological Science, Faculty of Agriculture, Tokyo University of Agriculture and Technology, 3-5-8 Saiwaicho, Fuchu, Tokyo 183, Japan.
Yopi
Sakano
Y
Y
D000595:Amino Acid Sequence; D001234:Aspergillus niger / Q000201:enzymology* / Q000235:genetics; D001236:Aspergillus oryzae / Q000378:metabolism; D001483:Base Sequence; D001665:Binding Sites; D002236:Carbohydrate Conformation; D002240:Carbohydrate Sequence; D003001:Cloning, Molecular; D016384:Consensus Sequence; D018076:DNA, Complementary / Q000235:genetics; D004271:DNA, Fungal / Q000235:genetics; D005656:Fungal Proteins / Q000096:biosynthesis / Q000235:genetics*; D005800:Genes, Fungal; D005936:Glucans / Q000737:chemistry / Q000378:metabolism; D006026:Glycoside Hydrolases / Q000096:biosynthesis / Q000235:genetics*; D008969:Molecular Sequence Data; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013045:Species Specificity; D013379:Substrate Specificity
D018076:DNA, Complementary; D004271:DNA, Fungal; D005656:Fungal Proteins; D005936:Glucans; D011993:Recombinant Fusion Proteins; C009109:pullulan; D006026:Glycoside Hydrolases; C047371:isopullulanase