A new group of exo-acting family 28 glycoside hydrolases of Aspergillus niger that are involved in pectin degradation.
The fungus Aspergillus niger is an industrial producer of pectin-degrading enzymes. The recent solving of the genomic sequence of A. niger allowed an inventory of the entire genome of the fungus for potential carbohydrate-degrading enzymes. By applying bioinformatics tools, 12 new genes, putatively encoding family 28 glycoside hydrolases, were identified. Seven of the newly discovered genes form a new gene group, which we show to encode exoacting pectinolytic glycoside hydrolases. This group includes four exo-polygalacturonan hydrolases (PGAX, PGXA, PGXB and PGXC) and three putative exo-rhamnogalacturonan hydrolases (RGXA, RGXB and RGXC). Biochemical identification using polygalacturonic acid and xylogalacturonan as substrates demonstrated that indeed PGXB and PGXC act as exo-polygalacturonases, whereas PGXA acts as an exo-xylogalacturonan hydrolase. The expression levels of all 21 genes were assessed by microarray analysis. The results from the present study demonstrate that exo-acting glycoside hydrolases play a prominent role in pectin degradation.
Martens-Uzunova
Elena S
ES
Section Fungal Genomics, Laboratory of Microbiology, Wageningen University, Dreijenlaan 2, 6703 HA Wageningen, The Netherlands.
Zandleven
Joris S
JS
Benen
Jaques A E
JA
Awad
Hanem
H
Kools
Harrie J
HJ
Beldman
Gerrit
G
Voragen
Alphons G J
AG
Van den Berg
Johan A
JA
Schaap
Peter J
PJ
D000115:Acetylesterase / Q000235:genetics / Q000378:metabolism; D000595:Amino Acid Sequence; D001234:Aspergillus niger / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics; D002241:Carbohydrates / Q000494:pharmacology; D004271:DNA, Fungal / Q000737:chemistry / Q000235:genetics; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D015966:Gene Expression Regulation, Fungal / Q000187:drug effects; D016681:Genome, Fungal / Q000235:genetics; D006026:Glycoside Hydrolases / Q000235:genetics / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D020411:Oligonucleotide Array Sequence Analysis; D010368:Pectins / Q000378:metabolism*; D010802:Phylogeny; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity
D002241:Carbohydrates; D004271:DNA, Fungal; D005656:Fungal Proteins; D007527:Isoenzymes; D012333:RNA, Messenger; D010368:Pectins; C096859:rhamnogalacturonan acetylesterase; D000115:Acetylesterase; D006026:Glycoside Hydrolases