Subsystem: D-Tagatose and Galactitol Utilization

This subsystem's description is:

== Catabolism of galactitol (Gat) and the ketoses D-tagatose (Tag) in enteric bacteria (ref.1):========

Catabolism starts with transport into the cells and concomitant phosphorylation through three enzyme II complexes or PTSs in which the three domains IIA, IIB, and IIC are either fused, or present as independent polypeptides as indicated. While IIGat requires the histidine protein HPr to accept the phosphate from the protein kinase enzyme I, IITag and IIFru have their own pseudo-HPr domain fused to the corresponding IIA-domains (TPr and FPr, respectively). The inactive IIBrsquo domain of IIFru is not present in IITag. The galactitol-PTS generates galactitol 1-phosphate (Gat1P), which is converted by a soluble dehydrogenase (GatD) to D-tagatose 6-phosphate (Tag6P); the normal phosphofructokinase PfkA (gene pfkA) in turn converts the latter into D-tagatose 1,6-bisphosphate (TagBP). This intermediate is hydrolyzed by the heterodimeric aldolase GatYZ to glyceraldehyde-phosphate (GAP) and dihydroxyacetone-phosphate (DHAP). The D-tagatose PTS generates D-tagatose 1-phosphate (Tag1P) which is converted by a Tag1P kinase (TagK) into TagBP. The tagatose pathway is analogous to that for fructose degradation via the kinase FruK and the aldolase FbaA

The gat operon in E. coli encodes a complete galactitol pathway, while the gat gene clusters in some other species (Salmonella enterica subsp. enterica serovar Typhi and Salmonella typhimurium) are interrupted by three additional tag genes - tagK, tagH and tagT.
The gat-tag genes are arranged in two operons. Both operons are controlled by the repressor GatR (encoded by gatR), and thus form a regulon. The new regulon now encodes two complete pathways for galactitol and D-tagatose degradation (Ref.1).
Degradation of both carbohydrates starts with transport into the cells and concomitant phosphorylation through three enzyme II complexes or PTSs in which the three domains IIA, IIB, and IIC are either fused, or present as independent polypeptides.
While IIGat requires the histidine protein HPr to accept the phosphate from the protein kinase enzyme I, IITag has it's own pseudo-HPr domain fused to the corresponding IIA-domains (TPr) - protein encoded by gene tagH.

*****Functional variants: **********************

1.0 - complete pathway for galactitol degradation;

1.x - some genes missed from the pathway for galactitol degradation;

2.0 - two complete pathways for galactitol and D-tagatose degradation (insertion of the tag genes into the gat-cluster);

2.x- some genes missed from the pathway for D-tagatose degradation

For more information, please check out the description and the additional notes tabs, below

DiagramFunctional RolesSubsystem SpreadsheetDescriptionAdditional NotesScenarios 

You have not provided a genome id to color the diagram with.

This diagram is not scaled.


Group Alias
Abbrev.Functional RoleReactionsScenario ReactionsGOLiterature
SubsetsColoring
collapsed
expanded


  
display  items per page
«first  «prevdisplaying 1 - 639 of 639next»  last»
Taxonomy Pattern 
Organism 
Domain
Variant [?] 
active
GatAGatBGatCGatRGat_prGatDGatYGatZTPKTagHTagTTagKPfkATE
«first  «prevdisplaying 1 - 639 of 639next»  last»
== Catabolism of galactitol (Gat) and the ketoses D-tagatose (Tag) in enteric bacteria (ref.1):========

Catabolism starts with transport into the cells and concomitant phosphorylation through three enzyme II complexes or PTSs in which the three domains IIA, IIB, and IIC are either fused, or present as independent polypeptides as indicated. While IIGat requires the histidine protein HPr to accept the phosphate from the protein kinase enzyme I, IITag and IIFru have their own pseudo-HPr domain fused to the corresponding IIA-domains (TPr and FPr, respectively). The inactive IIBrsquo domain of IIFru is not present in IITag. The galactitol-PTS generates galactitol 1-phosphate (Gat1P), which is converted by a soluble dehydrogenase (GatD) to D-tagatose 6-phosphate (Tag6P); the normal phosphofructokinase PfkA (gene pfkA) in turn converts the latter into D-tagatose 1,6-bisphosphate (TagBP). This intermediate is hydrolyzed by the heterodimeric aldolase GatYZ to glyceraldehyde-phosphate (GAP) and dihydroxyacetone-phosphate (DHAP). The D-tagatose PTS generates D-tagatose 1-phosphate (Tag1P) which is converted by a Tag1P kinase (TagK) into TagBP. The tagatose pathway is analogous to that for fructose degradation via the kinase FruK and the aldolase FbaA

The gat operon in E. coli encodes a complete galactitol pathway, while the gat gene clusters in some other species (Salmonella enterica subsp. enterica serovar Typhi and Salmonella typhimurium) are interrupted by three additional tag genes - tagK, tagH and tagT.
The gat-tag genes are arranged in two operons. Both operons are controlled by the repressor GatR (encoded by gatR), and thus form a regulon. The new regulon now encodes two complete pathways for galactitol and D-tagatose degradation (Ref.1).
Degradation of both carbohydrates starts with transport into the cells and concomitant phosphorylation through three enzyme II complexes or PTSs in which the three domains IIA, IIB, and IIC are either fused, or present as independent polypeptides.
While IIGat requires the histidine protein HPr to accept the phosphate from the protein kinase enzyme I, IITag has it's own pseudo-HPr domain fused to the corresponding IIA-domains (TPr) - protein encoded by gene tagH.

*****Functional variants: **********************

1.0 - complete pathway for galactitol degradation;

1.x - some genes missed from the pathway for galactitol degradation;

2.0 - two complete pathways for galactitol and D-tagatose degradation (insertion of the tag genes into the gat-cluster);

2.x- some genes missed from the pathway for D-tagatose degradation
*****Two D-tagatose 1,6-bisphosphate (TagBP)-specific aldolases:*************

Escherichia coli, Salmonella enterica, Klebsiella pneumoniae and Klebsiella oxytoca were found to contain two D-tagatose 1,6-bisphosphate (TagBP)-specific aldolases (Ref.2) involved in catabolism of galactitol (genes gatY and gatZ) and of N-acetyl-galactosamine and D-galactosamine (genes kbaY and kbaZ, also called agaY and agaZ).
The two aldolases were closely related (53.8% identical amino acids) and could substitute for each other in vivo. The catalytic subunits GatY or KbaY alone were sufficient to show aldolase activity. Although substantially shorter than other aldolases (285 amino acids, instead of 358 and 349 amino acids), these subunits contained most or all of the residues that have been identified as essential in substrate/product recognition and catalysis for class II aldolases. In contrast to these, both aldolases required subunits GatZ or KbaZ (420 amino acids) for full activity and for good in vivo and in vitro stability. The Z subunits alone did not show any aldolase activity. Close relatives of these new TagBP aldolases were found in several gram-negative and gram-positive bacteria.

GatY and AgaY correspond to two different but highly similar Tagatose-1,6-bisphosphate aldolases( class II aldolases) and both require for full activity and stability a second protein encoded by genes gatZ and agaZ, respectively (Ref.2).

**** Diagram:***************

The galactitol-PTS generates galactitol 1-phosphate (Gat1P), which is converted by a soluble dehydrogenase (GatD) to D-tagatose 6-phosphate (Tag6P); the normal phosphofructokinase PfkA (gene pfkA) in turn converts the latter into D-tagatose 1,6-bisphosphate (TagBP). This intermediate is hydrolyzed by the heterodimeric aldolase GatYZ to glyceraldehyde-phosphate (GAP) and dihydroxyacetone-phosphate (DHAP).

The D-tagatose PTS generates D-tagatose 1-phosphate (Tag1P) which is converted by a Tag1P kinase (TagK) into TagBP.


======REFERENCES===================

1. Shakeri-Garakani A, Brinkkotter A, Schmid K, Turgut S, Lengeler JW. The genes and enzymes for the catabolism of galactitol, D-tagatose, and related carbohydrates in Klebsiella oxytoca M5a1 and other enteric bacteria display convergent evolution. Mol Genet Genomics. 2004 Jul;271(6):717-28. Epub 2004 Jun 15. PMID: 15257457.

2. Brinkkötter A, Shakeri-Garakani A, Lengeler JW (2002) New class II D-tagatose-bisphosphate aldolases from enteric bacteria. Arch Microbiol 177:410–419.

3. Nobelmann B, Lengeler JW. Molecular analysis of the gat genes from Escherichia coli and of their roles in galactitol transport and metabolism.J Bacteriol. 1996 Dec;178(23):6790-5.PMID: 8955298.

4. Miallau L, Hunter WN, McSweeney SM, Leonard GA. Structures of Staphylococcus aureus D-tagatose-6-phosphate kinase implicate domain motions in specificity and mechanism.
J Biol Chem. 2007 Jul 6;282(27):19948-57. PMID: 17459874

Currently selected organism: none (open scenarios overview page)