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Literature summary for 2.4.1.207 extracted from
- Functional and chemical characterization of XAF a heat-stable plant polymer that activates xyloglucan endotransglucosylase/hydrolase (XTH) (2019), Ann. Bot., 124, 131-148 .
Activating Compound
| Activating Compound | Comment | Organism | Structure |
|---|---|---|---|
| XTH-activating factor | an endogenous cold-water-extractable, heat-stable polymer(s) (CHP) from cauliflower florets acts as an XTH-activating factor (XAF), promoting the XET activity of XTHs. The XTH-activating factors from plants desorb and thereby activate wall-bound XTHs. CHP specifically desorbed wall-bound XTHs, but not beta-glucosidases, phosphatases or peroxidases. CHP preparations from 25 angiosperms all possess XAF activity but have no consistent monosaccharide composition. Of 11 individual plant polymers tested, only gum arabic and tamarind xyloglucan are XAF-active, albeit less so than CHP. On gel-permeation chromatography, XAF-active cauliflower CHP elutes with a molecular weight of 7000-140000, although no specific sugar residue(s) co-elute exactly with XAF activity. Cauliflower XAF activity survives cold alkali and warm dilute TFA (which break ester and glycofuranosyl linkages, respectively), but is inactivated by hot 2 M TFA (which breaks glycopyranosyl linkages). Cauliflower XAF activity is remarkably stable to diverse glycanases and glycosidases, sugar composition of XAF-active CHPs from diverse plants and evaluation of XAF activity, detailed overview. The ability of CHP to solubilize XTHs from Arabidopsis cell walls is mimicked by NaCl and CaCl2. The effect plateaues above about 30 mM CaCl2, while the CHP effect does not plateau even at the highest concentration tested (1.8 mg/ml). The relative effect of CHP is greatest (34fold promotion) in the absence of CaCl2, but strong CHP effects (4.6 to 9.1fold promotion) and much higher absolute XET activities are still detected in the presence of 15 mM CaCl2, indicating synergy between CHP and the inorganic salt. Xyloglucan endoglucanase (XEG) shows some (moderate) ability to inactivate XAF. CHP has a stronger XAF effect on more dilute cell-wall suspensions | Arabidopsis thaliana |
Inhibitors
| Inhibitors | Comment | Organism | Structure |
|---|---|---|---|
| additional information | the xyloglucan endoglucanase (XEG) shows moderate inhibition of XTH-activating factor (XAF) activity. Cauliflower CHP exerts its XAF activity principally by (re-)solubilizing XTHs from surfaces (including cellulose, glass-fibre, glass and plastics) to which these enzymes tend to bind | Arabidopsis thaliana |
Localization
| Localization | Comment | Organism | GeneOntology No. | Textmining |
|---|---|---|---|---|
| cell wall | - |
Arabidopsis thaliana | 5618 | - |
Metals/Ions
| Metals/Ions | Comment | Organism | Structure |
|---|---|---|---|
| CaCl2 | the ability of cold-water-extractable, heat-stable polymers (CHPs) to solubilize XTHs from Arabidopsis cell walls is mimicked by NaCl and CaCl2. The effect plateaues above about 30 mM CaCl2, while the CHP effect does not plateau even at the highest concentration tested (1.8 mg/ml). The relative effect of CHP is greatest (34fold promotion) in the absence of CaCl2, but strong CHP effects (4.6 to 9.1fold promotion) and much higher absolute XET activities are still detected in the presence of 15 mM CaCl2, indicating synergy between CHP and the inorganic salt | Arabidopsis thaliana |  |
| NaCl | the ability of cold-water-extractable, heat-stable polymers (CHPs) to solubilize XTHs from Arabidopsis cell walls is mimicked by NaCl and CaCl2 | Arabidopsis thaliana | |
Organism
| Organism | UniProt | Comment | Textmining |
|---|---|---|---|
| Arabidopsis thaliana | - |
- |
- |
Source Tissue
| Source Tissue | Comment | Organism | Textmining |
|---|---|---|---|
| cell suspension culture | - |
Arabidopsis thaliana | - |
Substrates and Products (Substrate)
| Substrates | Comment Substrates | Organism | Products | Comment (Products) | Rev. | Reac. |
|---|---|---|---|---|---|---|
| additional information | [3H]XXXGol and tamarind xyloglucan are used as substrates in a radioactive enzyme assay to yield [3H]polysaccharide | Arabidopsis thaliana | ? | - |
- |
|
Synonyms
| Synonyms | Comment | Organism |
|---|---|---|
| XTH | - |
Arabidopsis thaliana |
| xyloglucan endotransglucosylase/hydrolase | - |
Arabidopsis thaliana |
Temperature Optimum [°C]
| Temperature Optimum [°C] | Temperature Optimum Maximum [°C] | Comment | Organism |
|---|---|---|---|
| 20 | - |
assay at | Arabidopsis thaliana |
pH Optimum
| pH Optimum Minimum | pH Optimum Maximum | Comment | Organism |
|---|---|---|---|
| 5.5 | - |
assay at | Arabidopsis thaliana |
General Information
| General Information | Comment | Organism |
|---|---|---|
| additional information | XTHs have a tendency to bind to various surfaces, including chromatography columns and cellulose. Bovine serum albumin (BSA) minimizes binding of solubilized XTHs to tube walls. BSA is the only agent which leads to the measured XET activity being proportional to the concentration of added enzyme: in all three types of plastic, reducing the concentration of the crude enzyme solution from 50% v/v to 15% v/v decrease the measured XET reaction rate by about 70%. Therefore, BSA at 2.5 mg/mL is included in the reaction mixture used in all subsequent XET assays | Arabidopsis thaliana |
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