Xylose metabolism in the anaerobic fungus Piromyces sp. strain E2 follows the bacterial pathway.
The anaerobic fungus Piromyces sp. strain E2 metabolizes xylose via xylose isomerase and d-xylulokinase as was shown by enzymatic and molecular analyses. This resembles the situation in bacteria. The clones encoding the two enzymes were obtained from a cDNA library. The xylose isomerase gene sequence is the first gene of this type reported for a fungus. Northern blot analysis revealed a correlation between mRNA and enzyme activity levels on different growth substrates. Furthermore, the molecular mass calculated from the gene sequence was confirmed by gel permeation chromatography of crude extracts followed by activity measurements. Deduced amino acid sequences of both genes were used for phylogenetic analysis. The xylose isomerases can be divided into two distinct clusters. The Piromyces sp. strain E2 enzyme falls into the cluster comprising plant enzymes and enzymes from bacteria with a low G+C content in their DNA. The d-xylulokinase of Piromyces sp. strain E2 clusters with the bacterial d-xylulokinases. The xylose isomerase gene was expressed in the yeast Saccharomyces cerevisiae, resulting in a low activity (25+/-13 nmol min(-1)mg protein(-1)). These two fungal genes may be applicable to metabolic engineering of Saccharomyces cerevisiae for the alcoholic fermentation of hemicellulosic materials.
Harhangi
Harry R
HR
Department of Microbiology, University of Nijmegen, Toernooiveld 1, Faculty of Science, 6525 ED, Nijmegen, The Netherlands.
Akhmanova
Anna S
AS
Emmens
Roul
R
van der Drift
Chris
C
de Laat
Wim T A M
WT
van Dijken
Johannes P
JP
Jetten
Mike S M
MS
Pronk
Jack T
JT
Op den Camp
Huub J M
HJ
D019747:Aldose-Ketose Isomerases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D000595:Amino Acid Sequence; D018628:Gene Dosage; D015723:Gene Library; D008969:Molecular Sequence Data; D008970:Molecular Weight; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D010802:Phylogeny; D020089:Piromyces / Q000201:enzymology* / Q000235:genetics; D011994:Recombinant Proteins / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000201:enzymology / Q000235:genetics; D017422:Sequence Analysis, DNA; D014158:Transcription, Genetic; D014170:Transformation, Genetic; D014994:Xylose / Q000378:metabolism*
D011994:Recombinant Proteins; D014994:Xylose; D017853:Phosphotransferases (Alcohol Group Acceptor); C032700:xylulokinase; D019747:Aldose-Ketose Isomerases; C023298:xylose isomerase