GONUTS has been updated to MW1.31 Most things seem to be working but be sure to report problems.
PMID:23019330
| Citation |
'Streb, S, Eicke, S and Zeeman, SC (2012) The Simultaneous Abolition of Three Starch Hydrolases Blocks Transient Starch Breakdown in Arabidopsis. J. Biol. Chem. ' |
|---|---|
| Abstract |
In this study we investigated which enzymes are involved in debranching amylopectin during transient starch degradation. Previous studies identified two debranching enzymes, isoamylase 3 (ISA3) and limit dextrinase (LDA), involved in this process. However, plants lacking both enzymes still degrade substantial amounts of starch. Thus, other enzymes/mechanisms must contribute to starch breakdown. We show that the chloroplastic α-amylase 3 (AMY3) also participates in starch degradation and provide evidence that all three enzymes can act directly at the starch granule surface. The isa3 mutant has a starch-excess phenotype, reflecting impaired starch breakdown. In contrast, removal of AMY3, LDA, or both enzymes together, has no impact on starch degradation. However, removal of AMY3 or LDA in addition to ISA3 enhances the starch-excess phenotype. In plants lacking all three enzymes, starch breakdown is effectively blocked and starch accumulates to the highest levels observed so far. This provides indirect evidence that the heteromultimeric debranching enzyme ISA1/ISA2 is not involved in starch breakdown. However, we illustrate that ISA1/ISA2 can hydrolyze small soluble branched glucans that accumulate when ISA3 and LDA are missing, albeit at a slow rate. Starch accumulation in the mutants correlates inversely with plant growth. |
| Links |
PubMed Online version:10.1074/jbc.M112.395244 |
| Keywords |
|
| edit table |
Significance
Annotations
| Gene product | Qualifier | GO Term | Evidence Code | with/from | Aspect | Extension | Notes | Status |
|---|---|---|---|---|---|---|---|---|
| GO:0004556: alpha-amylase activity |
ECO:0000315: |
F |
Figure 2 and Figure 3 |
complete | ||||
| GO:0004556: alpha-amylase activity |
ECO:0000314: |
F |
Figure 4 |
complete | ||||
|
enables |
GO:0004556: alpha-amylase activity |
ECO:0000315: mutant phenotype evidence used in manual assertion |
F |
Seeded From UniProt |
complete | |||
|
enables |
GO:0004556: alpha-amylase activity |
ECO:0000314: direct assay evidence used in manual assertion |
F |
Seeded From UniProt |
complete | |||
See also
References
See Help:References for how to manage references in GONUTS.
