Alpha-Amylase: An Overview with Special Discussion on Industrial Applications

Alpha-Amylase:,
An Overview with Special Discussion on Industrial Applications

Starch is constructed of glucose subunits linked to one another through glycosidic bonds.
Amylase is a group of enzymes capable of digesting these glycosidic linkages by hydrolyzing, or
splitting by the addition of a water molecule, the starch into smaller carbohydrate molecules like
glucose and maltose. It is best known for its function in beginning the chemical process of
digestion in the human body, converting complex carbohydrates into forms usable by the body.
However, with recent advances in biotechnology, the range of amylase applications has
significantly expanded. Detergent industries, brewing companies, food/agriculture industries,
textile industries, paper industries, and pharmaceuticals, all employ amylase during their
production. Over 80% of the global enzyme market is utilized in industrial settings and, of that,
amylase contributes approximately 25-33% to industrial application. This paper will provide an
overview of the genetics, structure, function, and regulation of alpha-amylase with a special
discussion on industrial applications.
Gottlieb Kirchhoff discovered the first starch-degrading enzyme in wheat in 1811, which
laid the groundwork for further research (Tiwari et al., 2015). Three major classes of amylases
that have been discovered since then are alpha- (α-), beta- (β-), and gamma- (γ-) amylase, based
on the way it attacks glycosidic bonds in starch and the structure of their products. α-amylase is
found in multiple forms in nature, two of which are found in the human body: salivary α-amylase
(ptyalin) and pancreatic α-amylase (amylopsin). First described in 1831 by Leuchs, ptyalin is one
of the most important enzymes found in saliva, constituting about 40-50% of salivary protein
(Tiwari et al., 2015). Ptyalin mixes with food and begins digestion until it reaches the stomach.
As digestion continues, the action of the enzyme depends on stomach acidity, how well food
mixes with the acid, and how quickly the stomach contents empty. About 30-40% of ingested
starches can be broken down during digestion in the stomach. Next, the pancreas secretes
amylopsin into the small intestines to aid in the digestion of the remaining starch until it reaches
the duodenum. The by-products of amylase hydrolysis are eventually broken down by other
enzymes into molecules of glucose, which are rapidly absorbed back into the body through the
intestinal wall (Aghajari et al., 2002). α-amylase can also be found in fungi, bacteria, and plants.
Fungi and bacteria are the primary sources of amylases used in industrial production because of
its low cost, consistency, and time and ease of modification. β- and γ-amylase are found in
yeasts, molds, bacteria, and plants (Tiwari et al., 2015). β-amylase is the form responsible for the
sweetness of ripening fruit (Amira El-Fallal et al., 2012).
3
The genes for salivary amylase (AMY 1A, 1B, and 1C) and pancreatic amylase (AMY
2A, 2B, and 2C) are located in a gene cluster on Chromosome 1(NCBI)(see Figure 1). It is an
abundant transcript expressed in the salivary glands of the oral cavity and pancreas, respectively.
The complete cDNA “contains 215 bp of 5′- untranslated region, 1536 bp of coding sequences,
and 33 bp of 3′-untranslated region. The coding region of salivary amylase cDNA differs from
pancreatic amylase by only 2%, but the 5′-untranslated region of the pancreatic amylase cDNA is
shorter” (Meisler & Ting, 1993).
Figure 1. Organization of amylase gene cluster on Chromosome 1. The positions of the five amylase genes are
shown with one pseudogene, AMYP1.
Image credit: Meisler & Ting, Critical Reviews in Oral Biology and Medicine, 1993.
It was suggested that pancreatic and salivary amylases were the product of different
genes. When amylase cDNAs were cloned from the pancreas and salivary glands in the 1980s,
the differences in sequence confirmed that statement. During isolation of the amylase genes and
comparison of their structures, a unique series of events discovered that salivary amylase
represents a more recent product of evolution. One interesting hypothesis for the evolution is that
the complex carbohydrates subjected to the action of salivary amylase produced sweet flavors in
the mouth and helped to identify nutritious food sources (Meisler & Ting, 1993). Evolutionarily,
dietary shifts have occurred partly because of the development of tools and technology, fire use,
and most recently the domestication of plants and animals. Starch, for example, has become an
important part of the human diet, making studies of the evolution of amylase in humans and
primate relatives crucial. Research suggests that since AMY1 exhibits a wide variation in copy
number, it correlates to different levels of dietary starch (Perry et al., 2007).
Amylase is composed of 512 amino acids with an average molecular weight of 57.6 kDa
(Tiwari et al., 2015). The structure of α-amylase consists of three domains: A, B, and C (see
Figure 2). Domain A (red) is the largest and most conserved in the various α-amylases. It is a
(β/α)8 super structure consisting of eight parallel β-sheets that form a barrel around eight α-
helices. Domain B (yellow), unlike Domain A, varies most in the type and number of amino acid
residues present, ranging from 44 to 133 residues. It is found protru

Need Help Writing an Essay?

Tell us about your assignment and we will find the best writer for your essay.

Write My Essay For Me