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Literature summary extracted from
- Functional roles of the hexamer organization of plant glutamate decarboxylase (2015), Biochim. Biophys. Acta, 1854, 1229-1237 .
Cloned(Commentary)
| EC Number | Cloned (Comment) | Organism |
|---|---|---|
| 4.1.1.15 | gene gad1, recombinant expression of wild-type and mutant enzymes in Escherichia coli strain BL21(DE3)pLysS | Arabidopsis thaliana |
Crystallization (Commentary)
| EC Number | Crystallization (Comment) | Organism |
|---|---|---|
| 4.1.1.15 | purified recombinant enzyme, X-ray diffraction structure determination and analysis | Arabidopsis thaliana |
Protein Variants
| EC Number | Protein Variants | Comment | Organism |
|---|---|---|---|
| 4.1.1.15 | additional information | removal of the first 24 N-terminal residues of AtGAD1 dramatically affects oligomerization by producing a dimeric enzyme. The deleted mutant retains decarboxylase activity, highlighting the dimeric nature of the basic structural unit of AtGAD1. The dimeric mutant enzyme forms a stable hexamer in the presence of Ca2+/CaM1. Binding of Ca2+/CaM1 appears to restore the hexamer species, since the gel filtration profiles of the mutant AtGAD1-DELTA1-24-Ca2+/CaM1 complex shows the same elution volume of the AtGAD1-Ca2+/CaM1 complex across the entire pH range. The AtGAD1-DELTA1-24 enzyme shows decreased thermal stability compared with the wild-type form | Arabidopsis thaliana |
| 4.1.1.15 | R24A | site-directed mutagenesis of key residue Arg24 in the N-terminal domain to Ala prevents hexamer formation of enzyme AtGAD1 in solution. The dimeric mutant enzyme forms a stable hexamer in the presence of Ca2+/ CaM1 | Arabidopsis thaliana |
Metals/Ions
| EC Number | Metals/Ions | Comment | Organism | Structure |
|---|---|---|---|---|
| 4.1.1.15 | Ca2+ | in plants, transient elevation of cytosolic Ca2+ in response to different types of stress is responsible for GAD activation via calmodulin. Binding of Ca2+/CaM1 abolishes the dissociation of the AtGAD1 oligomer | Arabidopsis thaliana |  |
Molecular Weight [Da]
| EC Number | Molecular Weight [Da] | Molecular Weight Maximum [Da] | Comment | Organism |
|---|---|---|---|---|
| 4.1.1.15 | 105000 | - |
homodimeric enzyme, gel filtration and native PAGE | Arabidopsis thaliana |
| 4.1.1.15 | 110000 | - |
truncated mutant enzyme AtGAD1-DELTA1-24, gel filtration | Arabidopsis thaliana |
| 4.1.1.15 | 342000 | - |
homohexameric enzyme, gel filtration and native PAGE | Arabidopsis thaliana |
Natural Substrates/ Products (Substrates)
| EC Number | Natural Substrates | Organism | Comment (Nat. Sub.) | Natural Products | Comment (Nat. Pro.) | Rev. | Reac. |
|---|---|---|---|---|---|---|---|
| 4.1.1.15 | L-glutamate | Arabidopsis thaliana | - |
4-aminobutanoate + CO2 | - |
? | |
Organism
| EC Number | Organism | UniProt | Comment | Textmining |
|---|---|---|---|---|
| 4.1.1.15 | Arabidopsis thaliana | Q42521 | - |
- |
Purification (Commentary)
| EC Number | Purification (Comment) | Organism |
|---|---|---|
| 4.1.1.15 | recombinant wild-type and mutant enzymes from Escherichia coli strain BL21(DE3)pLysS | Arabidopsis thaliana |
Substrates and Products (Substrate)
| EC Number | Substrates | Comment Substrates | Organism | Products | Comment (Products) | Rev. | Reac. |
|---|---|---|---|---|---|---|---|
| 4.1.1.15 | L-glutamate | - |
Arabidopsis thaliana | 4-aminobutanoate + CO2 | - |
? | |
Subunits
| EC Number | Subunits | Comment | Organism |
|---|---|---|---|
| 4.1.1.15 | homodimer | the basic structural unit of AtGAD1 is a homodimer | Arabidopsis thaliana |
| 4.1.1.15 | homohexamer | hexamer composed of a trimer of dimers. Hexamerization strongly contributes to the stability of the enzyme | Arabidopsis thaliana |
| 4.1.1.15 | More | in solution AtGAD1 is in a dimer-hexamer equilibrium. Binding of Ca2+/CaM1 abolishes the dissociation of the AtGAD1 oligomer. The AtGAD1N-terminal domain is critical for maintaining the oligomeric state. Arg24 in the N-terminal domain is a key residue. The oligomeric state of AtGAD1 is highly responsive to a number of experimental parameters and may have functional relevance in vivo in the light of the biphasic regulation of AtGAD1 activity by pH and Ca2+/CaM1 in plant cells. Tryptic peptide mapping. Effect of pH on the dissociation of hexameric AtGAD1 in the pH range 6.0-8.0, overview. A flexible and exposed stretch spanning residues 1-24 is the minimum region required for assembly of hexamer | Arabidopsis thaliana |
Synonyms
| EC Number | Synonyms | Comment | Organism |
|---|---|---|---|
| 4.1.1.15 | AtGAD1 | - |
Arabidopsis thaliana |
Temperature Optimum [°C]
| EC Number | Temperature Optimum [°C] | Temperature Optimum Maximum [°C] | Comment | Organism |
|---|---|---|---|---|
| 4.1.1.15 | 30 | - |
assay at | Arabidopsis thaliana |
Temperature Stability [°C]
| EC Number | Temperature Stability Minimum [°C] | Temperature Stability Maximum [°C] | Comment | Organism |
|---|---|---|---|---|
| 4.1.1.15 | 56 | - |
truncated enzyme mutant AtGAD1-DELTA1-24, T50 value | Arabidopsis thaliana |
| 4.1.1.15 | 70 | - |
wild-type enzyme, T50 value | Arabidopsis thaliana |
pH Optimum
| EC Number | pH Optimum Minimum | pH Optimum Maximum | Comment | Organism |
|---|---|---|---|---|
| 4.1.1.15 | 5.8 | - |
assay at | Arabidopsis thaliana |
Cofactor
| EC Number | Cofactor | Comment | Organism | Structure |
|---|---|---|---|---|
| 4.1.1.15 | Calmodulin | a unique feature of plant GAD is the presence of a calmodulin (CaM)-binding domain at its C-terminus. In plants, transient elevation of cytosolic Ca2+ in response to different types of stress is responsible for GAD activation via CaM | Arabidopsis thaliana | |
| 4.1.1.15 | pyridoxal 5'-phosphate | - |
Arabidopsis thaliana | |
General Information
| EC Number | General Information | Comment | Organism |
|---|---|---|---|
| 4.1.1.15 | evolution | the enzyme belongs to the fold type I family of PLP-enzymes | Arabidopsis thaliana |
| 4.1.1.15 | additional information | hexamerization strongly contributes to the stability of the enzyme. Plant GADs possess four conserved basic residues in their first 24 N-terminal amino acid region (H5,H15, R21, and R24 in AtGAD1). Two of the four residues (H15 and R24) are located at the interfaces between dimeric units | Arabidopsis thaliana |
| 4.1.1.15 | physiological function | compared to GADs from other organisms, plant GADs possess a unique feature, namely, the presence of a C-terminal calmodulin binding site (CaMBD). This characteristic confers plant GADs an additional regulatory mechanism by making them responsive to cytosolic calcium (Ca2+), thus revealing that at least two mechanisms exist, by which GAD activity can be stimulated in vitro and in vivo, namely, acidic pH and Ca2+/CaM. Transient elevation of cytosolic Ca2+ in response to different types of stress is responsible for GAD activation via CaM | Arabidopsis thaliana |
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