Difference Between Alpha and Beta Amylase

Key Difference – Alpha vs Beta Amylase
 

Both Alpha and Beta amylases are enzymes that catalyze the hydrolysis of starch into sugars. Alpha amylase acts on random locations along the starch chain whereas Beta amylase work from non-reducing ends in order to facilitate the breakdown of large polysaccharides. This is the key difference between Alpha amylase and Beta amylase. Further differences will be discussed in this article

What is Alpha Amylase (α-amylase)?

Amylase is an enzyme which aids the breakdown of large alpha-linked polysaccharides such as starch and glycogen to glucose and maltose. Alpha amylase is referred to as 1-4-a-D-glucan glucanohydrolase (EC 3.2.1.1.) according to the nomenclature of the commission of enzyme. It is found in humans and other mammals and also in seeds containing starch. It is also secreted by some fungi (ascomycetes,mbasidiomycetes) and bacteria (bacillus).

In the human body, amylase is most prominent in the pancreatic juice and saliva. Pancreatic α-amylase randomly cleaves the α (1,4) glycosidic linkages of amylose to yield dextrin , maltose or maltotriose. Amylase found in saliva is known as ptyalin and it breaks starch into maltose and dextrin.

Alpha amylase is a glycoprotein; a single polypeptide chain of about 475 residues has two free thiol groups, four disulfide bridges, and contains a tightly bound Ca2+. It exists in two forms namely PPAI and PPAII

Phenolic compounds, some plant extracts, and urea and other amide reagents can be considered as the inhibitors for Alpha amylase

Alpha amylase was discovered by Anselme Payen in 1833. Alpha amylase is used in ethanol production to break starch into fermentable sugars. It is also used in high fructose corn syrup production in order to produce shorter chain oligosaccharides. Alpha amylase (also known astermamyl) produced by Bacillus licheniform is especially used in starch removing detergent production.

Key Difference - Alpha vs Beta Amylase

Human salivary alpha-amylase

What is Beta Amylase (β-amylase)?

Beta amylase is an exoenzyme also known as 1-4-a-D- glucan maltohydrolase (EC 3.2.1.2.) which facilitates the hydrolysis of (1->4)-alpha- D glucosidic linkages in polysaccharides in order to remove successive maltose units from the non-reducing ends of the chains. Basically, it acts on starch, glycogen, and some polysaccharides.

Beta amylase is primarily found in seeds of higher plants, bacteria and fungi. Most of the β-amylases are monoeric enzymes; however, tetrameric amylase in sweet potato consists of four identical subunits. Each subunit consists of 8-barrel region. Cys96 is located at the entrance of this region. A small globular region is formed by long extended loops from β-strands.

Heavy metals, iodoacetamide, ascorbate, cyclohexaamylose and sulfhydryl reagents act as inhibitors for Beta amylase.

Beta amylase is used in fermentation in brewing and distilling industry, and saccharification of liquefied starch.

Difference Between Alpha and Beta Amylase

Barley Beta-Amylase

What is the difference between Alpha and Beta Amylase?

Site of Hydrolysis

Alpha amylase: Alpha amylase acts on random locations along the starch chain.

Beta amylase: Beta amylase acts from non-reducing end in order to facilitate the break down large polysaccharides.

Sources

Alpha amylase: Alpha amylase can be found in humans and some other mammals as well as in some plants and fungi.

Beta amylase: Beta amylase cannot be found in humans or animals.

Activity

Alpha amylase: Alpha amylase is assumed to act faster than Beta amylase.

Beta amylase: Beta amylase is assumed to be slower than Alpha amylase.

Status in Seed Germination

Alpha amylase: Alpha amylase appears once germination has begun.

Beta amylase: Beta amylase is present in an inactive form prior to germination.

Types

Alpha amylase: Alpha amylase exists in two forms.

Beta amylase: Beta amylase exists in single form.

Gene that Encode for the Enzyme

Alpha amylase: Human Alpha amylases are encoded by two loci amy1A, amy1B, amy1C (salivary) and amy2A, amy2B (pancreatic).

Beta amylase: Beta amylase is encoded by amyB.

Molecular Weight

Alpha amylase: Molecular weight (two types) varies from 51kDa to 54kDa.

Beta amylase: Molecular weight of Beta amylase is 223.8kDa.

Optimal pH

Alpha amylase: The optimal pH is 7.

Beta amylase: pH varies from 4 to 5.

Isoelectric Point

Alpha amylase:

PPAI  7.5

PPAII  6.4

Beta amylase: 5.17

Extinction Coefficient

Alpha amylase:  133,870 cm-1 M-1

Beta amylase: 388,640 cm-1 M-1

References

Alpha-amylase [Online]. Available: https://en.wikipedia.org/wiki/Alpha-amylase.

Amylase [Online]. Available: https://en.wikipedia.org/wiki/Amylase [Accessed June 24 2016].

Amylase, Alpha [Online]. Available: http://www.worthington-biochem.com/aa/ [Accessed June 24 2016].

Amylase, Beta [Online]. Available: http://www.worthington-biochem.com/ba/default.html.

Image Courtesy:
“2xfr b amylase” By A2-33 – Own work (CC BY-SA 3.0) via Commons Wikimedia
“Salivary alpha-amylase 1SMD” By Own work. – From PDB entry 1SMD.(Public Domain) via Commons Wikimedia