β-Amylase

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
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
PRIAMprofile
PDB structuresRCSB PDB PDBe PDBsum
Gene OntologyAmiGO / QuickGO
Search
PMCarticles
PubMedarticles
NCBIproteins

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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