Amylases are important hydrolase enzymes which have been widely used since many decades. These enzymes randomly cleave internal glycosidic linkages in starch molecules to hydrolyze them and yield dextrins and oligosaccharides. Among amylases α-Amylase is in maximum demand due to its wide range of applications in the industrial front. α-Amylase can be produced by plant or microbial sources. The ubiquitous nature, ease of production and broad spectrum of applications make α-Amylase an industrially important enzyme.

1. Amylases (Types, Sources, Mode of Action & Applications)
Amylases are important hydrolase enzymes which have been widely used since many decades.
These enzymes randomly cleave internal glycosidic linkages in starch molecules to hydrolyze
them and yield dextrins and oligosaccharides. Among amylases α-Amylase is in maximum
demand due to its wide range of applications in the industrial front. α-Amylase can be produced
by plant or microbial sources. The ubiquitous nature, ease of production and broad spectrum of
applications make α-Amylase an industrially important enzyme.
Types of Amylase
1. α-Amylase
α-Amylase (E.C.3.2.1.1) is a hydrolase enzyme that catalyses the hydrolysis of internal α-1, 4-
glycosidic linkages in starch to yield products like glucose and maltose. It is a calcium
metalloenzyme i.e. it depends on the presence of a metal co factor for its activity. The a-amylase
family is the largest family of glycoside hydrolases, transferases, and isomerases, comprising 30
different enzyme specificities. These enzymes are classified into four groups: endoamylases,
exoamylases, debranching enzymes, and transferases. Endo- hydrolases act on the interior of the
substrate molecule, whereas exo-hydrolases act on the terminal non reducing ends. α-Amylase
has become an enzyme of crucial importance due to its starch hydrolysis activity and the
activities that can be carried out owing to the hydrolysis. They are biodegradable and work at
milder conditions than chemical catalysts and hence preferred to the latter.
2. β – Amylase
β-Amylase (EC 3.2.1.2) is an exo-hydrolase enzyme that acts from the nonreducing end of a
polysaccharide chain by hydrolysis of α-1, 4-glucan linkages to yield successive maltose units.
Since it is unable to cleave branched linkages in branched polysaccharides such as glycogen or

2. amylopectin, the hydrolysis is incomplete and dextrin units remain. Primary sources of β-
Amylase are the seeds of higher plants and sweet potatoes. During ripening of fruits, β-Amylase
breaks down starch into maltose resulting in the sweetness of ripened fruit. In the industry it is
used for fermentation in brewing and distilling industry.
3. γ – Amylase
γ-Amylase (EC 3.2.1.3 ) cleaves α(1-6)glycosidic linkages, in addition to cleaving the last α(1-
4)glycosidic linkages at the nonreducing end of amylose and amylopectin, unlike the other forms
of amylase, yielding glucose. γ- amylase is most efficient in acidic environments and has an
optimum pH of 3.
Sources of amylase
a-Amylases are universally distributed throughout the plant, animal, and microbial kingdoms.
The enzymes from microbial sources have dominated applications in industrial processes.
Table: Sources of amylases
Source Example
Plant Family 1 a-amylases, Family 2 a-amylases and Family 3 a-amylases from
various monocotyledons, dicotyledons, and gymnosperms.
Bacteria Bacillus, Brevibacterium, Clostridium, Halomonas, Naxibacter, Nesterenkonia,
Paenibacillus, Pseudomonas, Streptomyces sp. Bacillus subtilis, Bacillus
stearothermophilus, Bacillus amyloliquefaciens, Bacillus licheniformis, Bacillus
acidocaldarius, Bifidobacterium bifidum, Bifidobacterium acerans, B.
licheniformis, and Bacillus halodurans, Anoxybacillus beppuensis, Bacillus
laterosporus, Bacillus acidicola, Chryseobacterium taeanense, Clostridium sp.
Microbacterium foliorum, Nesterenkonia sp, Thermococcus sp, Anoxybacillus

3. flavithermus
Fungi Acremonium, Aspergillus, Penicillium, Mucor, Neurospora, and Thermomyces
sp. Aspergillus niger, Aspergillus flavus, Aspergillus oryzae, Thermomyces
lanuginosus
Strain improvement is done to increase production as well as to improve the properties of the
amylases enzyme. The catalytic properties of amylases are determined by their 3-D structure.
Hence, enzyme properties can be altered by site-directed mutagenesis. Using this method, the
properties of an enzyme can be improved, by making it thermostable, reducing its dependence on
cofactors, or increasing its activity at low temperature. Studies on the cloning of the a-amylase
gene have been extensively carried out for hyperproduction. Below table shows some strategies
to improve the amylase activity
Table: Strain Improvement for amylases

4. Mode of action of amylases
Several aspects of amylase mode of action can be distinguished. A first aspect deals with the
action mechanism, i.e. the hydrolysis of the glucosidic bond on a molecular scale. All the
enzymes of GH family 13 retain the anomeric configuration and work according to the double
displacement mechanism. This is an acid-base catalysed reaction, requiring a proton donor and a
nucleophile, in which a glycosyl-enzyme intermediate is formed Typically, all endo-acting
amylases work according to this action mechanism. In contrast, exo-acting amylases, such as β-
amylases, are inverting amylases and work through the single displacement mechanism The
reaction proceeds through an oxocarbenium ion-like transition state. Another aspect of amylase
mode of action is that several models for amylase action pattern have been proposed, such as the
random action and the multiple attack action. Schematic representation of amylase action
patterns is given in figure below.
 Random manner
it is believed that α-amylases degrade the starch polymers in a random manner. This has also
been referred to as a single attack or multi-chain attack action. This mode of action implies that
all bonds are equally susceptible to hydrolysis. As a result, a rapid decrease in starch polymer
MW can be observed.
 Multiple attack action
Amylases with a multiple attack action cleave several glycosidic bonds successively after the
first (random) hydrolytic attack before dissociating from the substrate. The multiple attack action
is an intermediate between the single-chain and the multichain (or random) action. Multiple
attact action is defined as the degree of multiple attack (DMA) as the number of bonds broken

5. during the lifetime of an enzyme-substrate complex minus one (i.e. the initial random cleavage).
The multiple attack action is often referred to by the more generic term “processivity”
Figure: Schematic representation of amylase action patterns

6. Applications of a-Amylase
a-Amylases have very wide range of biotechnological applications in the textile, food,
pharmaceutical, detergent and various other industries. Due to latest developments in
biotechnology, the applications of a-amylases have been widened to other fields like clinical,
medicinal, and analytical chemistry.
Application
of Amylases
Detergent
Industry
Textile
Desizing
Mecinial &
clinical
chemistry
Paper
Industry
Strach
liquefication
Scarification
Bread &
Baking
Industry
Alcohol
Production
Glucose &
frutose
production

7. References:
Bijttebier, A., Goesaert, H., & Delcour, J. (2008). Amylase action pattern on starch polymers.
Biologia, 63(6), 989-999.
Sundarram, A., & Murthy, T. P. K. (2014). α-amylase production and applications: a review.
Journal of Applied & Environmental Microbiology, 2(4), 166-175.
Pandey, A., Negi, S., & Soccol, C. R. (Eds.). (2016). Current Developments in Biotechnology
and Bioengineering: Production, Isolation and Purification of Industrial Products. Elsevier.