| Structural highlights
5csy is a 2 chain structure with sequence from Arabidopsis thaliana. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance.
| | Method: | X-ray diffraction, Resolution 2.05Å |
| Ligands: | , , , , |
| Resources: | FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT |
Function
DPE1_ARATH Chloroplastic alpha-glucanotransferase involved in maltotriose metabolism. Probably uses maltotriose as substrate to transfer a maltosyl unit from one molecule to another, resulting in glucose and maltopentaose. The latter can then be further metabolized to maltose and maltotriose by beta-amylase. Required for normal starch degradation in leaves.[1] [2]
Publication Abstract from PubMed
The degradation of transitory starch in the chloroplast to provide fuel for the plant during the night requires a suite of enzymes that generate a series of short chain linear glucans. However, glucans of less than four glucose units are no longer substrates for these enzymes, whereas export from the plastid is only possible in the form of either maltose or glucose. In order to make use of maltotriose, which would otherwise accumulate, disproportionating enzyme 1 (DPE1; a 4-alpha-glucanotransferase) converts two molecules of maltotriose to a molecule of maltopentaose, which can now be acted on by the degradative enzymes, and one molecule of glucose that can be exported. We have determined the structure of the Arabidopsis plastidial DPE1 (AtDPE1), and, through ligand soaking experiments, we have trapped the enzyme in a variety of conformational states. AtDPE1 forms a homodimer with a deep, long, and open-ended active site canyon contained within each subunit. The canyon is divided into donor and acceptor sites with the catalytic residues at their junction; a number of loops around the active site adopt different conformations dependent on the occupancy of these sites. The "gate" is the most dynamic loop and appears to play a role in substrate capture, in particular in the binding of the acceptor molecule. Subtle changes in the configuration of the active site residues may prevent undesirable reactions or abortive hydrolysis of the covalently bound enzyme-substrate intermediate. Together, these observations allow us to delineate the complete AtDPE1 disproportionation cycle in structural terms.
Structural Dissection of the Maltodextrin Disproportionation Cycle of the Arabidopsis Plastidial Disproportionating Enzyme 1 (DPE1).,O'Neill EC, Stevenson CE, Tantanarat K, Latousakis D, Donaldson MI, Rejzek M, Nepogodiev SA, Limpaseni T, Field RA, Lawson DM J Biol Chem. 2015 Dec 11;290(50):29834-53. doi: 10.1074/jbc.M115.682245. Epub, 2015 Oct 26. PMID:26504082[3]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
References
- ↑ Critchley JH, Zeeman SC, Takaha T, Smith AM, Smith SM. A critical role for disproportionating enzyme in starch breakdown is revealed by a knock-out mutation in Arabidopsis. Plant J. 2001 Apr;26(1):89-100. PMID:11359613
- ↑ Stettler M, Eicke S, Mettler T, Messerli G, Hortensteiner S, Zeeman SC. Blocking the metabolism of starch breakdown products in Arabidopsis leaves triggers chloroplast degradation. Mol Plant. 2009 Nov;2(6):1233-46. doi: 10.1093/mp/ssp093. PMID:19946617 doi:http://dx.doi.org/10.1093/mp/ssp093
- ↑ O'Neill EC, Stevenson CE, Tantanarat K, Latousakis D, Donaldson MI, Rejzek M, Nepogodiev SA, Limpaseni T, Field RA, Lawson DM. Structural Dissection of the Maltodextrin Disproportionation Cycle of the Arabidopsis Plastidial Disproportionating Enzyme 1 (DPE1). J Biol Chem. 2015 Dec 11;290(50):29834-53. doi: 10.1074/jbc.M115.682245. Epub, 2015 Oct 26. PMID:26504082 doi:http://dx.doi.org/10.1074/jbc.M115.682245
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