β-amylase
Structure of barley beta-amylase. PDB 2xfr[1]
Identifiers
EC no.3.2.1.2
CAS no.9000-91-3
Databases
IntEnzIntEnz view
BRENDABRENDA entry
ExPASyNiceZyme view
KEGGKEGG entry
MetaCycmetabolic pathway
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PDB structuresRCSB PDB PDBe PDBsum
Gene OntologyAmiGO / QuickGO
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β-Amylase (EC 3.2.1.2, saccharogen amylase, glycogenase) is an enzyme with the systematic name 4-α-D-glucan maltohydrolase.[2][3][4] It catalyses the following reaction:

Hydrolysis of (1→4)-α-D-glucosidic linkages in polysaccharides so as to remove successive maltose units from the non-reducing ends of the chains

This enzyme acts on starch, glycogen and related polysaccharides and oligosaccharides producing beta-maltose by an inversion. Beta-amylase is found in bacteria, fungi, and plants; bacteria and cereal sources are the most heat stable. Working from the non-reducing end, β-amylase catalyzes the hydrolysis of the second α-1,4 glycosidic bond, cleaving off two glucose units (maltose) at a time. During the ripening of fruit, β-amylase breaks starch into maltose, resulting in the sweet flavor of ripe fruit.

β-amylase is present in an inactive form prior to seed germination. Many microbes also produce amylase to degrade extracellular starches.  Animal tissues do not contain β-amylase, although it may be present in microorganisms contained within the digestive tract. The optimum pH for β-amylase is 4.0–5.0[5] They belong to Glycoside hydrolase family 14.

See also

References

  1. ↑ Rejzek M, Stevenson CE, Southard AM, Stanley D, Denyer K, Smith AM, Naldrett MJ, Lawson DM, Field RA (March 2011). "Chemical genetics and cereal starch metabolism: structural basis of the non-covalent and covalent inhibition of barley β-amylase". Molecular BioSystems. 7 (3): 718–30. doi:10.1039/c0mb00204f. PMID 21085740.
  2. ↑ Balls AK, Walden MK, Thompson RR (March 1948). "A crystalline β-amylase from sweet potatoes". The Journal of Biological Chemistry. 173 (1): 9–19. doi:10.1016/S0021-9258(18)35550-9. PMID 18902365.
  3. ↑ French D (1960). "β-Amylases". In Boyer PD, Lardy H, Myrbaumlck K (eds.). The Enzymes. Vol. 4 (2nd ed.). New York: Academic Press. pp. 345–368.
  4. ↑ Manners DJ (1962). "Enzymic synthesis and degradation of starch and glycogen". Advances in Carbohydrate Chemistry. 17: 371–430. doi:10.1016/s0096-5332(08)60139-3. ISBN 9780120072170.
  5. ↑ "Amylase, Alpha" , I.U.B.: 3.2.1.11,4-α-D-Glucan glucanohydrolase.

Further reading

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