ectoine biosynthesis

MetaCyc:P101-PWY

Ectoine biosynthesis converts L-aspartate to L-ectoine through 4-phospho-L-aspartate, L-aspartate 4-semialdehyde, L-2,4-diaminobutanoate, and (2S)-4-acetamido-2-aminobutanoate.

Pathway type

compatible solute biosynthesis

Organism scope

Halomonas elongata NCBITaxon:2746

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Pathway network

33 nodes · 38 asserted directed edges

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Chemical / cofactor
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Solid arrow: mechanistic relation
Dashed arrow: membership, location or cofactor relation

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Components and activities

Declared biological components and source reaction directions
Node	Kind or role	Source direction
Halomonas elongata `NCBITaxon:2746`	taxon
aspartate kinase `EC:2.7.2.4`	molecular activity
aspartate-semialdehyde dehydrogenase `EC:1.2.1.11`	molecular activity
diaminobutyrate-2-oxoglutarate transaminase `EC:2.6.1.76`	molecular activity
diaminobutyrate acetyltransferase `EC:2.3.1.178`	molecular activity
ectoine synthase `EC:4.2.1.108`	molecular activity
L-aspartate `CHEBI:29991`	small molecule
ATP `CHEBI:30616`	small molecule
4-phospho-L-aspartate `CHEBI:57535`	small molecule
ADP `CHEBI:456216`	small molecule
NADPH `CHEBI:57783`	small molecule
H+ `CHEBI:15378`	small molecule
L-aspartate 4-semialdehyde `CHEBI:537519`	small molecule
phosphate `CHEBI:43474`	small molecule
NADP(+) `CHEBI:58349`	small molecule
L-glutamate `CHEBI:29985`	small molecule
L-2,4-diaminobutanoate `CHEBI:58761`	small molecule
2-oxoglutarate `CHEBI:16810`	small molecule
acetyl-CoA `CHEBI:57288`	small molecule
(2S)-4-acetamido-2-aminobutanoate `CHEBI:58929`	small molecule
CoA `CHEBI:57287`	small molecule
L-ectoine `CHEBI:58515`	small molecule
H2O `CHEBI:15377`	small molecule
Diaminobutyrate--2-oxoglutarate transaminase `UniProtKB:E1V7V7`	protein
cytoplasm `GO:0005737`	cellular component
pyridoxal 5'-phosphate(2-) `CHEBI:597326`	cofactor
L-2,4-diaminobutyric acid acetyltransferase `UniProtKB:O52249`	protein
Diaminobutyrate--2-oxoglutarate transaminase `UniProtKB:O52250`	protein
L-ectoine synthase `UniProtKB:O52251`	protein
ATP-dependent aspartate kinase reaction `RHEA:23777`	reaction	left to right
NADPH-dependent aspartate-semialdehyde dehydrogenase reaction `RHEA:24286`	reaction	right to left
biosynthetic diaminobutyrate transaminase reaction `RHEA:11162`	reaction	right to left
diaminobutanoate acetyltransferase reaction `RHEA:16902`	reaction	left to right
L-ectoine synthase reaction `RHEA:17282`	reaction	left to right

Mechanistic edges

Mechanistic edges and their cited evidence
Subject	Predicate and description	Object	Evidence
L-aspartate `CHEBI:29991`	consumes	ATP-dependent aspartate kinase reaction `RHEA:23777`	RHEA:23777 Source assertion: Rhea lists CHEBI:29991 on the substrates side of RHEA:23777 in this directed reaction. Source location `rdf:Description[@rdf:about='http://rdf.rhea-db.org/23777']/rh:substrates; rh:contains/rh:compound/rh:accession`
ATP `CHEBI:30616`	consumes	ATP-dependent aspartate kinase reaction `RHEA:23777`	RHEA:23777 Source assertion: Rhea lists CHEBI:30616 on the substrates side of RHEA:23777 in this directed reaction. Source location `rdf:Description[@rdf:about='http://rdf.rhea-db.org/23777']/rh:substrates; rh:contains/rh:compound/rh:accession`
ATP-dependent aspartate kinase reaction `RHEA:23777`	produces	ADP `CHEBI:456216`	RHEA:23777 Source assertion: Rhea lists CHEBI:456216 on the products side of RHEA:23777 in this directed reaction. Source location `rdf:Description[@rdf:about='http://rdf.rhea-db.org/23777']/rh:products; rh:contains/rh:compound/rh:accession`
ATP-dependent aspartate kinase reaction `RHEA:23777`	produces	4-phospho-L-aspartate `CHEBI:57535`	RHEA:23777 Source assertion: Rhea lists CHEBI:57535 on the products side of RHEA:23777 in this directed reaction. Source location `rdf:Description[@rdf:about='http://rdf.rhea-db.org/23777']/rh:products; rh:contains/rh:compound/rh:accession`
H+ `CHEBI:15378`	consumes	NADPH-dependent aspartate-semialdehyde dehydrogenase reaction `RHEA:24286`	RHEA:24286 Source assertion: Rhea lists CHEBI:15378 on the substrates side of RHEA:24286 in this directed reaction. Source location `rdf:Description[@rdf:about='http://rdf.rhea-db.org/24286']/rh:substrates; rh:contains/rh:compound/rh:accession`
4-phospho-L-aspartate `CHEBI:57535`	consumes	NADPH-dependent aspartate-semialdehyde dehydrogenase reaction `RHEA:24286`	RHEA:24286 Source assertion: Rhea lists CHEBI:57535 on the substrates side of RHEA:24286 in this directed reaction. Source location `rdf:Description[@rdf:about='http://rdf.rhea-db.org/24286']/rh:substrates; rh:contains/rh:compound/rh:accession`
NADPH `CHEBI:57783`	consumes	NADPH-dependent aspartate-semialdehyde dehydrogenase reaction `RHEA:24286`	RHEA:24286 Source assertion: Rhea lists CHEBI:57783 on the substrates side of RHEA:24286 in this directed reaction. Source location `rdf:Description[@rdf:about='http://rdf.rhea-db.org/24286']/rh:substrates; rh:contains/rh:compound/rh:accession`
NADPH-dependent aspartate-semialdehyde dehydrogenase reaction `RHEA:24286`	produces	phosphate `CHEBI:43474`	RHEA:24286 Source assertion: Rhea lists CHEBI:43474 on the products side of RHEA:24286 in this directed reaction. Source location `rdf:Description[@rdf:about='http://rdf.rhea-db.org/24286']/rh:products; rh:contains/rh:compound/rh:accession`
NADPH-dependent aspartate-semialdehyde dehydrogenase reaction `RHEA:24286`	produces	L-aspartate 4-semialdehyde `CHEBI:537519`	RHEA:24286 Source assertion: Rhea lists CHEBI:537519 on the products side of RHEA:24286 in this directed reaction. Source location `rdf:Description[@rdf:about='http://rdf.rhea-db.org/24286']/rh:products; rh:contains/rh:compound/rh:accession`
NADPH-dependent aspartate-semialdehyde dehydrogenase reaction `RHEA:24286`	produces	NADP(+) `CHEBI:58349`	RHEA:24286 Source assertion: Rhea lists CHEBI:58349 on the products side of RHEA:24286 in this directed reaction. Source location `rdf:Description[@rdf:about='http://rdf.rhea-db.org/24286']/rh:products; rh:contains/rh:compound/rh:accession`
L-glutamate `CHEBI:29985`	consumes	biosynthetic diaminobutyrate transaminase reaction `RHEA:11162`	RHEA:11162 Source assertion: Rhea lists CHEBI:29985 on the substrates side of RHEA:11162 in this directed reaction. Source location `rdf:Description[@rdf:about='http://rdf.rhea-db.org/11162']/rh:substrates; rh:contains/rh:compound/rh:accession`
L-aspartate 4-semialdehyde `CHEBI:537519`	consumes	biosynthetic diaminobutyrate transaminase reaction `RHEA:11162`	RHEA:11162 Source assertion: Rhea lists CHEBI:537519 on the substrates side of RHEA:11162 in this directed reaction. Source location `rdf:Description[@rdf:about='http://rdf.rhea-db.org/11162']/rh:substrates; rh:contains/rh:compound/rh:accession`
biosynthetic diaminobutyrate transaminase reaction `RHEA:11162`	produces	2-oxoglutarate `CHEBI:16810`	RHEA:11162 Source assertion: Rhea lists CHEBI:16810 on the products side of RHEA:11162 in this directed reaction. Source location `rdf:Description[@rdf:about='http://rdf.rhea-db.org/11162']/rh:products; rh:contains/rh:compound/rh:accession`
biosynthetic diaminobutyrate transaminase reaction `RHEA:11162`	produces	L-2,4-diaminobutanoate `CHEBI:58761`	RHEA:11162 Source assertion: Rhea lists CHEBI:58761 on the products side of RHEA:11162 in this directed reaction. Source location `rdf:Description[@rdf:about='http://rdf.rhea-db.org/11162']/rh:products; rh:contains/rh:compound/rh:accession`
acetyl-CoA `CHEBI:57288`	consumes	diaminobutanoate acetyltransferase reaction `RHEA:16902`	RHEA:16902 Source assertion: Rhea lists CHEBI:57288 on the substrates side of RHEA:16902 in this directed reaction. Source location `rdf:Description[@rdf:about='http://rdf.rhea-db.org/16902']/rh:substrates; rh:contains/rh:compound/rh:accession`
L-2,4-diaminobutanoate `CHEBI:58761`	consumes	diaminobutanoate acetyltransferase reaction `RHEA:16902`	RHEA:16902 Source assertion: Rhea lists CHEBI:58761 on the substrates side of RHEA:16902 in this directed reaction. Source location `rdf:Description[@rdf:about='http://rdf.rhea-db.org/16902']/rh:substrates; rh:contains/rh:compound/rh:accession`
diaminobutanoate acetyltransferase reaction `RHEA:16902`	produces	H+ `CHEBI:15378`	RHEA:16902 Source assertion: Rhea lists CHEBI:15378 on the products side of RHEA:16902 in this directed reaction. Source location `rdf:Description[@rdf:about='http://rdf.rhea-db.org/16902']/rh:products; rh:contains/rh:compound/rh:accession`
diaminobutanoate acetyltransferase reaction `RHEA:16902`	produces	CoA `CHEBI:57287`	RHEA:16902 Source assertion: Rhea lists CHEBI:57287 on the products side of RHEA:16902 in this directed reaction. Source location `rdf:Description[@rdf:about='http://rdf.rhea-db.org/16902']/rh:products; rh:contains/rh:compound/rh:accession`
diaminobutanoate acetyltransferase reaction `RHEA:16902`	produces	(2S)-4-acetamido-2-aminobutanoate `CHEBI:58929`	RHEA:16902 Source assertion: Rhea lists CHEBI:58929 on the products side of RHEA:16902 in this directed reaction. Source location `rdf:Description[@rdf:about='http://rdf.rhea-db.org/16902']/rh:products; rh:contains/rh:compound/rh:accession`
(2S)-4-acetamido-2-aminobutanoate `CHEBI:58929`	consumes	L-ectoine synthase reaction `RHEA:17282`	RHEA:17282 Source assertion: Rhea lists CHEBI:58929 on the substrates side of RHEA:17282 in this directed reaction. Source location `rdf:Description[@rdf:about='http://rdf.rhea-db.org/17282']/rh:substrates; rh:contains/rh:compound/rh:accession`
L-ectoine synthase reaction `RHEA:17282`	produces	H2O `CHEBI:15377`	RHEA:17282 Source assertion: Rhea lists CHEBI:15377 on the products side of RHEA:17282 in this directed reaction. Source location `rdf:Description[@rdf:about='http://rdf.rhea-db.org/17282']/rh:products; rh:contains/rh:compound/rh:accession`
L-ectoine synthase reaction `RHEA:17282`	produces	L-ectoine `CHEBI:58515`	RHEA:17282 Source assertion: Rhea lists CHEBI:58515 on the products side of RHEA:17282 in this directed reaction. Source location `rdf:Description[@rdf:about='http://rdf.rhea-db.org/17282']/rh:products; rh:contains/rh:compound/rh:accession`
aspartate kinase `EC:2.7.2.4`	catalyzes	ATP-dependent aspartate kinase reaction `RHEA:23777`	RHEA:23776 Source assertion: Rhea associates EC:2.7.2.4 with the reaction family containing RHEA:23777. Source location `rh:ec`
aspartate-semialdehyde dehydrogenase `EC:1.2.1.11`	catalyzes	NADPH-dependent aspartate-semialdehyde dehydrogenase reaction `RHEA:24286`	RHEA:24284 Source assertion: Rhea associates EC:1.2.1.11 with the reaction family containing RHEA:24286. Source location `rh:ec`
diaminobutyrate-2-oxoglutarate transaminase `EC:2.6.1.76`	catalyzes	biosynthetic diaminobutyrate transaminase reaction `RHEA:11162`	RHEA:11160 Source assertion: Rhea associates EC:2.6.1.76 with the reaction family containing RHEA:11162. Source location `rh:ec` PMID:9864317 conversion of ASA to DABA by transamination with l-glutamate Source location `PubMed Abstract`
diaminobutyrate acetyltransferase `EC:2.3.1.178`	catalyzes	diaminobutanoate acetyltransferase reaction `RHEA:16902`	RHEA:16901 Source assertion: Rhea associates EC:2.3.1.178 with the reaction family containing RHEA:16902. Source location `rh:ec` PMID:9864317 DABA acetyltransferase catalyzed acetylation of DABA Source location `PubMed Abstract`
ectoine synthase `EC:4.2.1.108`	catalyzes	L-ectoine synthase reaction `RHEA:17282`	RHEA:17281 Source assertion: Rhea associates EC:4.2.1.108 with the reaction family containing RHEA:17282. Source location `rh:ec` PMID:9864317 Ectoine synthase catalyzed circularization of ADABA to ectoine Source location `PubMed Abstract`
biosynthetic diaminobutyrate transaminase reaction `RHEA:11162`	precedes	diaminobutanoate acetyltransferase reaction `RHEA:16902`	MetaCyc:P101-PWY Source assertion: MetaCyc pathway ordering places RHEA:11162 before RHEA:16902 in this pathway. Shared intermediate: CHEBI:58761. Source location `Pathway/reaction-ordering and reaction-layout; Rhea-to-MetaCyc cross-references`
diaminobutanoate acetyltransferase reaction `RHEA:16902`	precedes	L-ectoine synthase reaction `RHEA:17282`	MetaCyc:P101-PWY Source assertion: MetaCyc pathway ordering places RHEA:16902 before RHEA:17282 in this pathway. Shared intermediate: CHEBI:58929. Source location `Pathway/reaction-ordering and reaction-layout; Rhea-to-MetaCyc cross-references`
ATP-dependent aspartate kinase reaction `RHEA:23777`	precedes	NADPH-dependent aspartate-semialdehyde dehydrogenase reaction `RHEA:24286`	MetaCyc:P101-PWY Source assertion: MetaCyc pathway ordering places RHEA:23777 before RHEA:24286 in this pathway. Shared intermediate: CHEBI:57535. Source location `Pathway/reaction-ordering and reaction-layout; Rhea-to-MetaCyc cross-references`
NADPH-dependent aspartate-semialdehyde dehydrogenase reaction `RHEA:24286`	precedes	biosynthetic diaminobutyrate transaminase reaction `RHEA:11162`	MetaCyc:P101-PWY Source assertion: MetaCyc pathway ordering places RHEA:24286 before RHEA:11162 in this pathway. Shared intermediate: CHEBI:537519. Source location `Pathway/reaction-ordering and reaction-layout; Rhea-to-MetaCyc cross-references`
Diaminobutyrate--2-oxoglutarate transaminase `UniProtKB:E1V7V7`	enables	biosynthetic diaminobutyrate transaminase reaction `RHEA:11162`	UniProtKB:E1V7V7 Source assertion: UniProt annotates UniProtKB:E1V7V7 with catalytic activity for the reaction family of RHEA:11162. Annotation evidence: ECO:0000305; organism taxon: NCBITaxon:768066. Source location `comments[commentType='CATALYTIC ACTIVITY'].reaction.reactionCrossReferences`
Diaminobutyrate--2-oxoglutarate transaminase `UniProtKB:E1V7V7`	located_in	cytoplasm `GO:0005737`	UniProtKB:E1V7V7 Source assertion: UniProt locates UniProtKB:E1V7V7 in Cytoplasm (SL-0086, mapped by UniProt to GO:0005737). Annotation evidence: ECO:0000250. Source location `comments[commentType='SUBCELLULAR LOCATION'].subcellularLocations; UniProt location vocabulary GO mapping`
Diaminobutyrate--2-oxoglutarate transaminase `UniProtKB:E1V7V7`	has_cofactor	pyridoxal 5'-phosphate(2-) `CHEBI:597326`	UniProtKB:E1V7V7 Source assertion: UniProt lists CHEBI:597326 as a cofactor of UniProtKB:E1V7V7 (evidence: ECO:0000250). Source location `comments[commentType='COFACTOR'].cofactors and note`
L-2,4-diaminobutyric acid acetyltransferase `UniProtKB:O52249`	enables	diaminobutanoate acetyltransferase reaction `RHEA:16902`	UniProtKB:O52249 Source assertion: UniProt annotates UniProtKB:O52249 with catalytic activity for the reaction family of RHEA:16902. Annotation evidence: ECO:0000269; organism taxon: NCBITaxon:768066. Source location `comments[commentType='CATALYTIC ACTIVITY'].reaction.reactionCrossReferences`
Diaminobutyrate--2-oxoglutarate transaminase `UniProtKB:O52250`	enables	biosynthetic diaminobutyrate transaminase reaction `RHEA:11162`	UniProtKB:O52250 Source assertion: UniProt annotates UniProtKB:O52250 with catalytic activity for the reaction family of RHEA:11162. Annotation evidence: ECO:0000269; organism taxon: NCBITaxon:768066. Source location `comments[commentType='CATALYTIC ACTIVITY'].reaction.reactionCrossReferences`
Diaminobutyrate--2-oxoglutarate transaminase `UniProtKB:O52250`	has_cofactor	pyridoxal 5'-phosphate(2-) `CHEBI:597326`	UniProtKB:O52250 Source assertion: UniProt lists CHEBI:597326 as a cofactor of UniProtKB:O52250 (evidence: ECO:0000269). Source location `comments[commentType='COFACTOR'].cofactors and note`
L-ectoine synthase `UniProtKB:O52251`	enables	L-ectoine synthase reaction `RHEA:17282`	UniProtKB:O52251 Source assertion: UniProt annotates UniProtKB:O52251 with catalytic activity for the reaction family of RHEA:17282. Annotation evidence: ECO:0000269; organism taxon: NCBITaxon:768066. Source location `comments[commentType='CATALYTIC ACTIVITY'].reaction.reactionCrossReferences`

References

MetaCyc:P101-PWY MetaCyc ectoine biosynthesis pathway (source version: 22.5)
RHEA:23777 Rhea L-aspartate kinase direction (source version: 139)
RHEA:24286 Rhea biosynthetic aspartate-semialdehyde dehydrogenase direction (source version: 139)
RHEA:11162 Rhea biosynthetic diaminobutyrate transaminase direction (source version: 139)
RHEA:16902 Rhea diaminobutanoate acetyltransferase direction (source version: 139)
RHEA:17282 Rhea L-ectoine synthase direction (source version: 139)
PMID:9864317 Ono et al., Journal of Bacteriology, 1999
RHEA:23776 RHEA:23776 authority record (source version: 139)
RHEA:24284 RHEA:24284 authority record (source version: 139)
RHEA:11160 RHEA:11160 authority record (source version: 139)
RHEA:16901 RHEA:16901 authority record (source version: 139)
RHEA:17281 RHEA:17281 authority record (source version: 139)
UniProtKB:E1V7V7 UniProtKB:E1V7V7 authority record (source version: 2026_03)
UniProtKB:O52249 UniProtKB:O52249 authority record (source version: 2026_03)
UniProtKB:O52250 UniProtKB:O52250 authority record (source version: 2026_03)
UniProtKB:O52251 UniProtKB:O52251 authority record (source version: 2026_03)

Curation history

2026-10-05T06:25:52Z codex
- EDIT — Review causal chemistry and add sourced molecular context
  Reviewed the entire record against MetaCyc 22.5 native pathway XML (including nested pathways), Rhea 139 explicit sides and directions, ENZYME 02-Sep-2026, PubMed records, and reviewed UniProt 2026_03 annotations within the record's taxon scope. Replaced generated structured-source quotations with source_assertion and source_locator. Typed molecular activities and participants. Reaction count 5 to 5; 0 directed-ID corrections; 4 protein annotations, 2 cofactor annotations and 1 sourced locations. All Rhea reaction substrate/product sets checked against independent Rhea authority; native pathway leaf coverage and source exceptions recorded in reports/causal_graph_review/metacyc-review.json. Full source URLs, versions and byte hashes are in metacyc-sources.json. All 50 MetaCyc records passed native schema validation; six targeted chemistry/evidence regression tests passed. Missing protein or cofactor annotations are not treated as biological absence; qualifications and exclusions are preserved in the ledger.
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