Alpha-glucosidase

From Infogalactic: the planetary knowledge core
Jump to: navigation, search
Alpha-glucosidase
310px
Alpha-glucosidase hexamer, Sulfolobus solfataricus
Identifiers
EC number 3.2.1.20
CAS number Template:CAS
Databases
IntEnz IntEnz view
BRENDA BRENDA entry
ExPASy NiceZyme view
KEGG KEGG entry
MetaCyc metabolic pathway
PRIAM profile
PDB structures RCSB PDB PDBe PDBsum
File:Glykogen.svg
Glycogen structure segment.
Maltose

Alpha-glucosidase (EC 3.2.1.20, maltase, glucoinvertase, glucosidosucrase, maltase-glucoamylase, alpha-glucopyranosidase, glucosidoinvertase, alpha-D-glucosidase, alpha-glucoside hydrolase, alpha-1,4-glucosidase, alpha-D-glucoside glucohydrolase) is a glucosidase located in the brush border of the small intestine that acts upon 1,4-alpha bonds.[1][2][3][4][5][6] This is in contrast to beta-glucosidase. Alpha-glucosidase breaks down starch and disaccharides to glucose. Maltase, a similar enzyme that cleaves maltose, is nearly functionally equivalent.

Other glucosidases include:

Mechanism

Alpha-glucosidase hydrolyzes terminal non-reducing 1-4 linked alpha- glucose residues to release a single alpha- glucose molecule.[7] Alpha-glucosidase is a carbohydrate-hydrolase that releases alpha-glucose as opposed to beta-glucose. Beta-glucose residues can be released by glucoamylase, a functionally similar enzyme. The substrate selectivity of alpha-glucosidase is due to subsite affinities of the enzyme’s active site.[8] Two proposed mechanisms include a nucleophilic displacement and an oxocarbenium ion intermediate.[8]

File:Catalytic Reaction for a-glucosidase.png
Example of an alpha-glucosidase catalyzed reaction
  • Rhodnius prolixus, a blood-sucking insect, forms hemozoin (Hz) during digestion of host hemoglobin. Hemozoin synthesis is dependent on the substrate binding site of alpha-glucosidase.[9]
  • Trout liver alpha-glucosidases were extracted and characterized. It was shown that for one of the trout liver alpha-glucosidases maximum activity of the enzyme was increased by 80% during exercise in comparison to a resting trout. This change was shown to correlate to an activity increase for liver glycogen phosphorylase. It is proposed that alpha-glucosidase in the glucosidic path plays an important part in complementing the phosphorolytic pathway in the liver’s metabolic response to energy demands of exercise.[10]
  • Yeast and rat small intestinal alpha-glucosidases have been shown to be inhibited by several groups of flavonoids.[11]

Structure

File:Alpha-glucosidase in complex with maltose and NAD+.png
Alpha-glucosidase in complex with maltose and NAD+

Alpha-glucosidases can potentially be split, according to primary structure, into two families.[8] The gene coding for human lysosomal alpha-glucosidase is about 20 kb long and its structure has been cloned and confirmed.[12]

  • Human lysosomal alpha-glucosidase has been studied for the significance of the Asp-518 and other residues in proximity of the enzyme’s active site. It was found that substituting Asp-513 with Glu-513 interferes with posttranslational modification and intracellular transport of alpha-glucosidase’s precursor. Additionally, the Trp-516 and Asp-518 residues have been deemed critical for the enzyme’s catalytic functionality.[13]
  • Kinetic changes in alpha-glucosidase have been shown to be induced by denaturants such as guanidinium chloride (GdmCl) and SDS solutions. These denaturants cause loss of activity and conformational change. A loss of enzyme activity occurs at much lower concentrations of denaturant than required for conformational changes. This leads to a conclusion that the enzyme’s active site conformation is less stable than the whole enzyme conformation in response to the two denaturants.[14]

Disease relevance

  • Pompe Disease: a disorder in which alpha-glucosidase is deficient. In 2006, the drug Alglucosidase alfa became the first released treatment for Pompe Disease and acts as an analog to alpha-glucosidase.[15] Further studies of alglucosidase alfa revealed that iminosugars exhibit inhibition of the enzyme. It was found that one compound molecule binds to a single enzyme molecule. It was shown that 1-deoxynojirimycin (DNJ) would bind the strongest of the sugars tested and blocked the active site of the enzyme almost entirely. The studies enhanced knowledge of the mechanism by which alpha-glucosidase binds to imino sugars.[16]
  • Diabetes: Acarbose, an alpha-glucosidase inhibitor, competitively and reversibly inhibits alpha-glucosidase in the intestines. This inhibition lowers the rate of glucose absorption through delayed carbohydrate digestion and extended digestion time. Acarbose may have the capability to stop developing diabetic symptoms.[17] Hence, alpha-glucosidase inhibitors (like Acarbose) are used as anti-diabetic drugs in combination with other anti-diabetic drugs. Luteolin has been found to be a strong inhibitor of alpha-glucosidase. The compound can inhibit the enzyme up to 36% with a concentration of 0.5 mg/ml.[18] As of 2016, this substance is being tested in rats, mice and cell culture.
  • Azoospermia: Diagnosis of azoospermia has potential to be aided by measurement of alpha-glucosidase activity in seminal plasma. Activity in the seminal plasma corresponds to the functionality of the epididymis.[19]
  • Anti-Viral Agents: Many animal viruses possess an outer envelope composed of viral glycoproteins. These are often required for the viral life cycle and utilize cellular machinery for synthesis. Inhibitors of alpha-glucosidase show that the enzyme is involved in the pathway for N-glycans for viruses such as HIV and human hepatitis B virus (HBV). Inhibition of alpha-glucosidase can prevent fusion of HIV and secretion of HBV.[20]

See also

References

<templatestyles src="Reflist/styles.css" />

Cite error: Invalid <references> tag; parameter "group" is allowed only.

Use <references />, or <references group="..." />

de:Maltase-Glucoamylase

  1. ↑ alpha-Glucosidases at the US National Library of Medicine Medical Subject Headings (MeSH)
  2. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  3. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  4. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  5. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  6. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  7. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  8. ↑ 8.0 8.1 8.2 Lua error in package.lua at line 80: module 'strict' not found.
  9. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  10. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  11. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  12. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  13. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  14. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  15. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  16. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  17. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  18. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  19. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  20. ↑ Lua error in package.lua at line 80: module 'strict' not found.
Retrieved from "https://infogalactic.com/w/index.php?title=Alpha-glucosidase&oldid=720598920"