O81852 · AKH2_ARATH
- ProteinBifunctional aspartokinase/homoserine dehydrogenase 2, chloroplastic
- GeneAKHSDH2
- StatusUniProtKB reviewed (Swiss-Prot)
- Amino acids916 (go to sequence)
- Protein existenceEvidence at protein level
- Annotation score5/5
Function
function
Bifunctional aspartate kinase and homoserine dehydrogenase that catalyzes the first and the third steps toward the synthesis of lysine, methionine and threonine from aspartate.
Catalytic activity
- L-homoserine + NADP+ = H+ + L-aspartate 4-semialdehyde + NADPHThis reaction proceeds in the backward direction.
Cofactor
Note: A sodium ion is seen in the structure; a metal ion may subtly affect the relative position of the nucleotide-binding region to influence enzyme activity, and could increase the stability of the enzyme.
Activity regulation
Threonine interaction with Gln-443 leads to inhibition of aspartate kinase activity and facilitates the binding of a second threonine on Gln-524, leading to a partial inhibition of homoserine dehydrogenase activity (25% of activity remaining at saturation with threonine). Homoserine dehydrogenase activity is also partially inhibited by cysteine (15% of activity remaining at saturation with cysteine). No synergy between threonine and cysteine for the inhibition. 13-fold activation of aspartate kinase activity by cysteine, isoleucine, valine, serine and alanine at 2.5 mM and 4-fold activation by leucine at 2.5 mM, but no activation of homoserine dehydrogenase activity.
Kinetics
KM | SUBSTRATE | pH | TEMPERATURE[C] | NOTES | EVIDENCE | |
---|---|---|---|---|---|---|
11.6 mM | aspartate for the aspartokinase activity | in the presence of 40 mM ATP | ||||
6.15 mM | aspartate for the aspartokinase activity | 8.0 | in the presence of 200 uM NADPH 20 mM ATP | |||
1.5 mM | aspartate for the aspartokinase activity | 8.0 | in the presence of 200 uM NADPH, 20 mM ATP a saturating concentration of alanine | |||
26.4 mM | aspartate for the aspartokinase activity | in the presence of 100 mM ATP 0.5 mM threonine | ||||
5.5 mM | ATP for the aspartokinase activity | in the presence of 50 mM aspartate | ||||
2.2 mM | ATP for the aspartokinase activity | 8.0 | in the presence of 200 uM NADPH 50 mM aspartate | |||
0.42 mM | ATP for the aspartokinase activity | 8.0 | in the presence of 200 uM NADPH, 50 mM aspartate a saturating concentration of alanine | |||
5.2 mM | homoserine for the reverse reaction of the homoserine dehydrogenase activity | in the presence of 1 mM NADP | ||||
1.4 mM | aspartate semialdehyde for the forward reaction of the homoserine dehydrogenase activity | in the presence of NADPH | ||||
311 μM | aspartate semialdehyde for the forward reaction of the homoserine dehydrogenase activity | 8.0 | in the presence of 150 mM KCl 200 uM NADPH | |||
24.5 mM | homoserine for the reverse reaction of the homoserine dehydrogenase activity | in the presence of 1 mM NADP 60 mM threonine | ||||
166.1 μM | NADP for the reverse reaction of the homoserine dehydrogenase activity | in the presence of 50 mM homoserine | ||||
676.1 μM | NADP for the reverse reaction of the homoserine dehydrogenase activity | in the presence of 100 mM homoserine 60 mM threonine |
Vmax | pH | TEMPERATURE[C] | NOTES | EVIDENCE | |
---|---|---|---|---|---|
5.4 μmol/min/mg | toward aspartylhydroxamate for the aspartokinase activity | ||||
165 μmol/min/mg | toward aspartate semialdehyde for the forward reaction of the homoserine dehydrogenase activity | ||||
18.8 μmol/min/mg | toward NADPH for the reverse reaction of the homoserine dehydrogenase activity |
Pathway
Amino-acid biosynthesis; L-lysine biosynthesis via DAP pathway; (S)-tetrahydrodipicolinate from L-aspartate: step 1/4.
Amino-acid biosynthesis; L-methionine biosynthesis via de novo pathway; L-homoserine from L-aspartate: step 1/3.
Amino-acid biosynthesis; L-methionine biosynthesis via de novo pathway; L-homoserine from L-aspartate: step 3/3.
Amino-acid biosynthesis; L-threonine biosynthesis; L-threonine from L-aspartate: step 1/5.
Amino-acid biosynthesis; L-threonine biosynthesis; L-threonine from L-aspartate: step 3/5.
Features
Showing features for binding site, active site.
Type | ID | Position(s) | Description | |||
---|---|---|---|---|---|---|
Binding site | 568 | NAD+ (UniProtKB | ChEBI) | ||||
Sequence: I | ||||||
Binding site | 568 | NADP+ (UniProtKB | ChEBI) | ||||
Sequence: I | ||||||
Binding site | 568 | NADPH (UniProtKB | ChEBI) | ||||
Sequence: I | ||||||
Binding site | 600 | NADP+ (UniProtKB | ChEBI) | ||||
Sequence: K | ||||||
Binding site | 649 | NAD+ (UniProtKB | ChEBI) | ||||
Sequence: T | ||||||
Binding site | 649 | NADP+ (UniProtKB | ChEBI) | ||||
Sequence: T | ||||||
Binding site | 649 | NADPH (UniProtKB | ChEBI) | ||||
Sequence: T | ||||||
Binding site | 673 | NADP+ (UniProtKB | ChEBI) | ||||
Sequence: K | ||||||
Binding site | 673 | NADPH (UniProtKB | ChEBI) | ||||
Sequence: K | ||||||
Binding site | 700 | Na+ (UniProtKB | ChEBI) | ||||
Sequence: E | ||||||
Binding site | 703 | Na+ (UniProtKB | ChEBI) | ||||
Sequence: V | ||||||
Binding site | 705 | Na+ (UniProtKB | ChEBI) | ||||
Sequence: A | ||||||
Binding site | 707 | Na+ (UniProtKB | ChEBI) | ||||
Sequence: L | ||||||
Binding site | 758 | NADP+ (UniProtKB | ChEBI) | ||||
Sequence: G | ||||||
Binding site | 761 | L-homoserine (UniProtKB | ChEBI) | ||||
Sequence: E | ||||||
Binding site | 761 | NADP+ (UniProtKB | ChEBI) | ||||
Sequence: E | ||||||
Binding site | 772 | L-homoserine (UniProtKB | ChEBI) | ||||
Sequence: D | ||||||
Active site | 776 | Proton donor | ||||
Sequence: K | ||||||
Binding site | 893 | NAD+ (UniProtKB | ChEBI) | ||||
Sequence: G | ||||||
Binding site | 893 | NADP+ (UniProtKB | ChEBI) | ||||
Sequence: G | ||||||
Binding site | 893 | NADPH (UniProtKB | ChEBI) | ||||
Sequence: G |
GO annotations
Aspect | Term | |
---|---|---|
Cellular Component | chloroplast | |
Cellular Component | chloroplast stroma | |
Molecular Function | aspartate kinase activity | |
Molecular Function | ATP binding | |
Molecular Function | homoserine dehydrogenase activity | |
Molecular Function | metal ion binding | |
Molecular Function | NAD+ binding | |
Molecular Function | NADP binding | |
Biological Process | homoserine biosynthetic process | |
Biological Process | lysine biosynthetic process via diaminopimelate | |
Biological Process | methionine biosynthetic process | |
Biological Process | threonine biosynthetic process |
Keywords
- Molecular function
- Biological process
- Ligand
Enzyme and pathway databases
Names & Taxonomy
Protein names
- Recommended nameBifunctional aspartokinase/homoserine dehydrogenase 2, chloroplastic
- Short namesAK-HD 2; AK-HSDH 2
- Alternative names
Including 2 domains:
- Recommended nameAspartokinase
- EC number
- Alternative names
- Recommended nameHomoserine dehydrogenase
- EC number
Gene names
Organism names
- Strain
- Taxonomic lineageEukaryota > Viridiplantae > Streptophyta > Embryophyta > Tracheophyta > Spermatophyta > Magnoliopsida > eudicotyledons > Gunneridae > Pentapetalae > rosids > malvids > Brassicales > Brassicaceae > Camelineae > Arabidopsis
Accessions
- Primary accessionO81852
- Secondary accessions
Proteomes
Organism-specific databases
Genome annotation databases
Subcellular Location
Phenotypes & Variants
Features
Showing features for mutagenesis.
Type | ID | Position(s) | Description | |||
---|---|---|---|---|---|---|
Mutagenesis | 441 | Loss of threonine sensitivity for the aspartokinase activity and decreased inhibition of homoserine dehydrogenase activity by threonine. | ||||
Sequence: I → A | ||||||
Mutagenesis | 443 | Loss of threonine sensitivity for the aspartokinase activity and decreased inhibition of homoserine dehydrogenase activity by threonine. | ||||
Sequence: Q → A | ||||||
Mutagenesis | 522 | No effect on the inhibition of aspartokinase activity by threonine, but decreased inhibition of homoserine dehydrogenase activity by threonine. | ||||
Sequence: I → A | ||||||
Mutagenesis | 524 | No effect on the inhibition of aspartokinase activity by threonine, but decreased inhibition of homoserine dehydrogenase activity by threonine. | ||||
Sequence: Q → A |
Variants
We now provide the "Disease & Variants" viewer in its own tab.
The viewer provides 61 variants from UniProt as well as other sources including ClinVar and dbSNP.
PTM/Processing
Features
Showing features for transit peptide, chain.
Type | ID | Position(s) | Description | |||
---|---|---|---|---|---|---|
Transit peptide | 1-87 | Chloroplast | ||||
Sequence: MATLKPSFTVSPPNSNPIRFGSFPPQCFLRVPKPRRLILPRFRKTTGGGGGLIRCELPDFHLSATATTVSGVSTVNLVDQVQIPKGE | ||||||
Chain | PRO_0000245845 | 88-916 | Bifunctional aspartokinase/homoserine dehydrogenase 2, chloroplastic | |||
Sequence: MWSVHKFGGTCVGNSQRIRNVAEVIINDNSERKLVVVSAMSKVTDMMYDLIRKAQSRDDSYLSALEAVLEKHRLTARDLLDGDDLASFLSHLHNDISNLKAMLRAIYIAGHASESFSDFVAGHGELWSAQMLSYVVRKTGLECKWMDTRDVLIVNPTSSNQVDPDFGESEKRLDKWFSLNPSKIIIATGFIASTPQNIPTTLKRDGSDFSAAIMGALLRARQVTIWTDVDGVYSADPRKVNEAVILQTLSYQEAWEMSYFGANVLHPRTIIPVMRYNIPIVIRNIFNLSAPGTIICQPPEDDYDLKLTTPVKGFATIDNLALINVEGTGMAGVPGTASDIFGCVKDVGANVIMISQASSEHSVCFAVPEKEVNAVSEALRSRFSEALQAGRLSQIEVIPNCSILAAVGQKMASTPGVSCTLFSALAKANINVRAISQGCSEYNVTVVIKREDSVKALRAVHSRFFLSRTTLAMGIVGPGLIGATLLDQLRDQAAVLKQEFNIDLRVLGITGSKKMLLSDIGIDLSRWRELLNEKGTEADLDKFTQQVHGNHFIPNSVVVDCTADSAIASRYYDWLRKGIHVITPNKKANSGPLDQYLKLRDLQRKSYTHYFYEATVGAGLPIISTLRGLLETGDKILRIEGICSGTLSYLFNNFVGDRSFSEVVTEAKNAGFTEPDPRDDLSGTDVARKVIILARESGLKLDLADLPIRSLVPEPLKGCTSVEEFMEKLPQYDGDLAKERLDAENSGEVLRYVGVVDAVNQKGTVELRRYKKEHPFAQLAGSDNIIAFTTTRYKDHPLIVRGPGAGAQVTAGGIFSDILRLASYLGAPS |
Proteomic databases
PTM databases
Expression
Gene expression databases
Structure
Family & Domains
Features
Showing features for region, domain.
Type | ID | Position(s) | Description | |||
---|---|---|---|---|---|---|
Region | 88-336 | Aspartokinase | ||||
Sequence: MWSVHKFGGTCVGNSQRIRNVAEVIINDNSERKLVVVSAMSKVTDMMYDLIRKAQSRDDSYLSALEAVLEKHRLTARDLLDGDDLASFLSHLHNDISNLKAMLRAIYIAGHASESFSDFVAGHGELWSAQMLSYVVRKTGLECKWMDTRDVLIVNPTSSNQVDPDFGESEKRLDKWFSLNPSKIIIATGFIASTPQNIPTTLKRDGSDFSAAIMGALLRARQVTIWTDVDGVYSADPRKVNEAVILQTL | ||||||
Region | 337-562 | Interface | ||||
Sequence: SYQEAWEMSYFGANVLHPRTIIPVMRYNIPIVIRNIFNLSAPGTIICQPPEDDYDLKLTTPVKGFATIDNLALINVEGTGMAGVPGTASDIFGCVKDVGANVIMISQASSEHSVCFAVPEKEVNAVSEALRSRFSEALQAGRLSQIEVIPNCSILAAVGQKMASTPGVSCTLFSALAKANINVRAISQGCSEYNVTVVIKREDSVKALRAVHSRFFLSRTTLAMGI | ||||||
Domain | 412-487 | ACT 1 | ||||
Sequence: VEGTGMAGVPGTASDIFGCVKDVGANVIMISQASSEHSVCFAVPEKEVNAVSEALRSRFSEALQAGRLSQIEVIPN | ||||||
Domain | 493-570 | ACT 2 | ||||
Sequence: AVGQKMASTPGVSCTLFSALAKANINVRAISQGCSEYNVTVVIKREDSVKALRAVHSRFFLSRTTLAMGIVGPGLIGA | ||||||
Region | 563-916 | Homoserine dehydrogenase | ||||
Sequence: VGPGLIGATLLDQLRDQAAVLKQEFNIDLRVLGITGSKKMLLSDIGIDLSRWRELLNEKGTEADLDKFTQQVHGNHFIPNSVVVDCTADSAIASRYYDWLRKGIHVITPNKKANSGPLDQYLKLRDLQRKSYTHYFYEATVGAGLPIISTLRGLLETGDKILRIEGICSGTLSYLFNNFVGDRSFSEVVTEAKNAGFTEPDPRDDLSGTDVARKVIILARESGLKLDLADLPIRSLVPEPLKGCTSVEEFMEKLPQYDGDLAKERLDAENSGEVLRYVGVVDAVNQKGTVELRRYKKEHPFAQLAGSDNIIAFTTTRYKDHPLIVRGPGAGAQVTAGGIFSDILRLASYLGAPS |
Sequence similarities
In the N-terminal section; belongs to the aspartokinase family.
In the C-terminal section; belongs to the homoserine dehydrogenase family.
Keywords
- Domain
Phylogenomic databases
Family and domain databases
Sequence & Isoform
- Sequence statusComplete
- Sequence processingThe displayed sequence is further processed into a mature form.
This entry describes 2 isoforms produced by Alternative splicing.
O81852-1
This isoform has been chosen as the canonical sequence. All positional information in this entry refers to it. This is also the sequence that appears in the downloadable versions of the entry.
- Name1
- Length916
- Mass (Da)100,250
- Last updated1998-11-01 v1
- Checksum7ECD984DAFC97C4F
O81852-2
- Name2
- Differences from canonical
- 837-916: LRYVGVVDAVNQKGTVELRRYKKEHPFAQLAGSDNIIAFTTTRYKDHPLIVRGPGAGAQVTAGGIFSDILRLASYLGAPS → RLFTTNVFPFDQCDHILTIYICM
Features
Showing features for alternative sequence.
Type | ID | Position(s) | Description | |||
---|---|---|---|---|---|---|
Alternative sequence | VSP_019798 | 837-916 | in isoform 2 | |||
Sequence: LRYVGVVDAVNQKGTVELRRYKKEHPFAQLAGSDNIIAFTTTRYKDHPLIVRGPGAGAQVTAGGIFSDILRLASYLGAPS → RLFTTNVFPFDQCDHILTIYICM |
Keywords
- Coding sequence diversity
- Technical term
Sequence databases
Nucleotide Sequence | Protein Sequence | Molecule Type | Status | |
---|---|---|---|---|
AL024486 EMBL· GenBank· DDBJ | CAA19688.1 EMBL· GenBank· DDBJ | Genomic DNA | ||
AL161551 EMBL· GenBank· DDBJ | CAB78973.1 EMBL· GenBank· DDBJ | Genomic DNA | ||
CP002687 EMBL· GenBank· DDBJ | AEE84219.1 EMBL· GenBank· DDBJ | Genomic DNA | ||
CP002687 EMBL· GenBank· DDBJ | AEE84220.1 EMBL· GenBank· DDBJ | Genomic DNA | ||
BX827863 EMBL· GenBank· DDBJ | - | mRNA | No translation available. |