This view shows enzymes only for those organisms listed below, in the list of taxa known to possess the pathway. If an enzyme name is shown in bold, there is experimental evidence for this enzymatic activity.
|Superclasses:||Degradation/Utilization/Assimilation → Carbohydrates Degradation → Sugars Degradation → Trehalose Degradation|
Expected Taxonomic Range:
There are several alternative pathways for the degradation of trehalose. Depending on the organism, trehalose may enter the cell either through a permease, in which case it remains unmodified, or it may be transported by a phosphotransferase system (PTS), resulting in the phoshorylated trehalose-6-phosphate form. Degradation then proceeds by different mechanisms: Unmodified trehalose may be degraded by a hydrolyzing trehalase (see trehalose degradation II (trehalase)), or it may be split by the action of a trehalose phosphorylase (seetrehalose degradation IV and trehalose degradation V). Likewise, trehalose-6-phosphate may be either hydrolyzed by trehalose-6-phosphate hydrolase (see trehalose degradation I (low osmolarity)) or it could be attacked by a trehalose-6-phosphate phosphorylase (see trehalose degradation III).
Trehalose degradation utilizing a trehalose-6-phosphate is found in many bacteria. It was studied extensively in the Gram-negative bacterium Escherichia coli (under conditions of low osmolarity). However, it has also been demonstrated in some Gram-positive bacteria, including Paenibacillus popilliae and Bacillus subtilis [Bhumiratana74, Helfert95].
While Escherichia coli only synthesizes trehalose under conditions of high osmolarity, it can degrade the sugar under conditions of both low and high osmolarity. In fact, Escherichia coli can grow with trehalose as the sole carbon source. Different pathways are employed under different osmolarity conditions.
Since no trehalose biosynthesis is happening in low osmolarity conditions, the only source of trehalose is external supply. Trehalose is imported into the cell by a PTS system for trehalose, which is composed of the EIIAGlc of the glucose-PTS, and a trehalose-specific EIITre, encoded by the treB gene. Trehalose is phosphorylated during the transport and enters the cytoplasm as trehalose-6-phosphate.
The resulting trehalose-6-phosphate is then hydrolyzed by trehalose-6-phosphate hydrolase, which is encoded by the treC gene, yielding glucose and glucose-6-phosphate. The free glucose is phosphorylated further by glucokinase into a second molecule of glucose-6-phosphate, and both glucose-6-phosphate moieties enter glycolysis [Klein95, Rimmele94].
Unification Links: EcoCyc:TREDEGLOW-PWY
Helfert95: Helfert C, Gotsche S, Dahl MK (1995). "Cleavage of trehalose-phosphate in Bacillus subtilis is catalysed by a phospho-alpha-(1-1)-glucosidase encoded by the treA gene." Mol Microbiol 16(1);111-120. PMID: 7651129
DiazMejia09: Diaz-Mejia JJ, Babu M, Emili A (2009). "Computational and experimental approaches to chart the Escherichia coli cell-envelope-associated proteome and interactome." FEMS Microbiol Rev 33(1);66-97. PMID: 19054114
Kawai05: Kawai S, Mukai T, Mori S, Mikami B, Murata K (2005). "Hypothesis: structures, evolution, and ancestor of glucose kinases in the hexokinase family." J Biosci Bioeng 99(4);320-30. PMID: 16233797
Lunin04: Lunin VV, Li Y, Schrag JD, Iannuzzi P, Cygler M, Matte A (2004). "Crystal structures of Escherichia coli ATP-dependent glucokinase and its complex with glucose." J Bacteriol 186(20);6915-27. PMID: 15466045
Magnani92: Magnani M, Bianchi M, Casabianca A, Stocchi V, Daniele A, Altruda F, Ferrone M, Silengo L (1992). "A recombinant human 'mini'-hexokinase is catalytically active and regulated by hexose 6-phosphates." Biochem J 285 ( Pt 1);193-9. PMID: 1637300
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