EglC, a new endoglucanase from Aspergillus niger with major activity towards xyloglucan.
A novel gene, eglC, encoding an endoglucanase, was cloned from Aspergillus niger. Transcription of eglC is regulated by XlnR, a transcriptional activator that controls the degradation of polysaccharides in plant cell walls. EglC is an 858-amino-acid protein and contains a conserved C-terminal cellulose-binding domain. EglC can be classified in glycoside hydrolase family 74. No homology to any of the endoglucanases from Trichoderma reesei was found. In the plant cell wall xyloglucan is closely linked to cellulose fibrils. We hypothesize that the EglC cellulose-binding domain anchors the enzyme to the cellulose chains while it is cleaving the xyloglucan backbone. By this action it may contribute to the degradation of the plant cell wall structure together with other enzymes, including hemicellulases and cellulases. EglC is most active towards xyloglucan and therefore is functionally different from the other two endoglucanases from A. niger, EglA and EglB, which exhibit the greatest activity towards beta-glucan. Although the mode of action of EglC is not known, this enzyme represents a new enzyme function involved in plant cell wall polysaccharide degradation by A. niger.
Hasper
Alinda A
AA
Molecular Genetics of Industrial Microorganisms Section, Wageningen University, NL-6703 HA Wageningen, The Netherlands.
Dekkers
Ester
E
van Mil
Marc
M
van de Vondervoort
Peter J I
PJ
de Graaff
Leo H
LH
D000595:Amino Acid Sequence; D001234:Aspergillus niger / Q000201:enzymology* / Q000254:growth & development; D002480:Cellulase / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism*; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism; D015966:Gene Expression Regulation, Fungal; D005936:Glucans; D008969:Molecular Sequence Data; D011134:Polysaccharides / Q000378:metabolism*; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism; D017422:Sequence Analysis, DNA; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic; D014990:Xylans
D005656:Fungal Proteins; D005936:Glucans; D011134:Polysaccharides; D012097:Repressor Proteins; D015534:Trans-Activators; C115443:XlnR protein, Aspergillus; D014990:Xylans; C071237:CreA protein, Aspergillus nidulans; C029353:xyloglucan; D002480:Cellulase