Amylase: Difference between revisions

Discovered and isolated by [http://en.wikipedia.org/wiki/Anselme_Payen Anselme Payen] in 1833, amylase was the first enzyme to be discovered<ref name="book">Yamamoto T.1988. Handbook of Amylases and Related Enzymes: Their Sources, Isolation Methods, Properties and Applications. Osaka Japan: Pergamon Press .</ref>. Amylases are hydrolases, acting on α-1,4-glycosidic bonds<ref name="Path">PMID:9541387</ref>. They can be further subdivided into α,β and γ amylases<ref name="book"/>. α-Amylase is an enzyme that acts as a catalyst for the hydrolysis of alpha-linked polysaccharides into α-anomeric products<ref name="Main">PMID:11226887</ref>. The enzyme can be derived from a variety of sources, each with different characteristics. α-Amylase found within the human body serves as the enzyme active in pancreatic juice and salvia. α-Amylase is not only essential in human physiology but has a number of important biotechnological functions in various processing industries<ref name="Path"/>.

Shown as 1hvx is the structure of the thermostable α-amylase of ''Bacillus stearothermophilus'' (BSTA)<ref name="Main"/>. BSTA is comprised of a single polypeptide chain. This chain is folded into three domains: A, B and C. These domains are generally found on all α-amylase enzymes. The <scene name='Sandbox_182/Domain_aa/1'>A domain </scene>constitutes the core structure, with a (β/α)bar rel.The <scene name='Sandbox_182/Domain_a/1'> B domain</scene> consists of a sheet of four anti-parallel β-strands with a pair of anti-parallel  β-strands. Long loops are observed between the β-strands.  Located within the B domain is the <scene name='Sandbox_182/Trio/1'>binding site</scene> for Ca²⁺-Na⁺-Ca²⁺. <scene name='Sandbox_182/Domain_c/1'>Domain C </scene>consisting of eight β-strands assembled into a globular unit forming a Greek key motif.  It also holds the <scene name='Sandbox_182/Caiii/1'>third </scene>Ca²⁺ binding site in association with domain A. Positioned on the C-terminal side of the β-strands of the (β/α)barrel in domain A is the active site.  The catalytic residues involved for the BSTA active site are Asp234, Glu264, and Asp331. The residues are identical to other α-amylases, yet there are positional differences which reflect the flexible nature of catalytic resides.

<scene name='Sandbox_182/Trio/1'>CaII and CaI with Na</scene> found in the interior of domain B and <scene name='Sandbox_182/Caiii/1'>CaIII </scene>at the interface of domain A and C, constitute the metal ion binding sites. All α-amylases contain one strongly conserved Ca²⁺ ion for structural integrity and enzymatic activity.<ref name="chloride">PMID: 12021442</ref> CaI is consistent in α-amylases, however there are structural differences between the linear trio of CaI, CaII and Na in other enzymes. CaIII acts as a bridge between two loops, one from Aα6 of domain A, and one between Cβ1 and Cβ2 of domain C.