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2xfr b amylase.png
Structure of barley beta-amylase. PDB 2xfr[1]
EC number
CAS number 9000-91-3
IntEnz IntEnz view
ExPASy NiceZyme view
MetaCyc metabolic pathway
PRIAM profile
PDB structures RCSB PDB PDBe PDBsum
Gene Ontology AmiGO / QuickGO

Beta-amylase (EC, saccharogen amylase, glycogenase) is an enzyme with the systematic name 4-alpha-D-glucan maltohydrolase.[2][3][4] This enzyme catalyses the following chemical reaction

Hydrolysis of (1->4)-alpha-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]

See also[edit]


  1. ^ Rejzek, M.; Stevenson, C. E.; Southard, A. M.; Stanley, D.; Denyer, K.; Smith, A. M.; Naldrett, M. J.; Lawson, D. M.; Field, R. A. (2011). "Chemical genetics and cereal starch metabolism: Structural basis of the non-covalent and covalent inhibition of barley β-amylase". Molecular BioSystems. 7 (3): 718–730. doi:10.1039/c0mb00204f. PMID 21085740. 
  2. ^ Balls, A.K.; Walden, M.K.; Thompson, R.R. (1948). "A crystalline β-amylase from sweet potatoes". J. Biol. Chem. 173: 9–19. 
  3. ^ French, D. (1960). "β-Amylases". In Boyer, P.D.; Lardy, H.; Myrbaumlck, K. The Enzymes. 4 (2nd ed.). New York: Academic Press. pp. 345–368. 
  4. ^ Manners, D.J. (1962). "Enzymic synthesis and degradation of starch and glycogen". Adv. Carbohydr. Chem. 17: 371–430. doi:10.1016/s0096-5332(08)60139-3. 
  5. ^ "Amylase, Alpha" , I.U.B.:,4-α-D-Glucan glucanohydrolase.

External links[edit]