The α-galactosidase type A gene aglA from Aspergillus niger encodes a fully functional α-N-acetylgalactosaminidase.
Two genes in the genome of Aspergillus niger, aglA and aglB, have been assigned to encode for α-d-galactosidases variant A and B. However, analyses of primary and 3D structures based on structural models of these two enzymes revealed significant differences in their active centers suggesting important differences in their specificity for the hydrolyzed carbohydrates. To test this unexpected finding, a large screening of libraries from 42 strains of filamentous fungi succeeded in identifying an enzyme from A. niger CCIM K2 that exhibited both α-galactosidase and α-N-acetylgalactosaminidase activities, with the latter activity predominating. The enzyme protein was sequenced, and its amino acid sequence could be unequivocally assigned to the enzyme encoded the aglA gene. Enzyme activity measurements and substrate docking clearly demonstrated the preference of the identified enzyme for α-N-acetyl-d-galactosaminide over α-d-galactoside. Thus, we provide evidence that the α-galactosidase type A gene aglA from A. niger in fact encodes a fully functional α-N-acetylgalactosaminidase using a retaining mechanism.
Kulik
Natallia
N
Center for Biocatalysis and Biotransformation, Institute of Systems Biology and Ecology, Academy of Sciences of the Czech Republic, Zámek 136, CZ37333 Nové Hrady, Czech Republic.
Weignerová
Lenka
L
Filipi
Tomás
T
Pompach
Petr
P
Novák
Petr
P
Mrázek
Hynek
H
Slámová
Kristyna
K
Bezouska
Karel
K
Kren
Vladimír
V
Ettrich
Rüdiger
R
D000595:Amino Acid Sequence; D001234:Aspergillus niger / Q000201:enzymology* / Q000235:genetics; D005800:Genes, Fungal; D008958:Models, Molecular; D008969:Molecular Sequence Data; D017386:Sequence Homology, Amino Acid; D000519:alpha-Galactosidase / Q000235:genetics*; D048809:alpha-N-Acetylgalactosaminidase / Q000737:chemistry / Q000235:genetics*
D000519:alpha-Galactosidase; D048809:alpha-N-Acetylgalactosaminidase