Maltase is defined as an enzyme that catalyzes the disaccharide maltose hydrolysis to the simple sugar glucose. This enzyme is present in bacteria, yeast, and plants, and it is thought to be generated by cells of the mucous membrane lining the intestinal wall in humans and other vertebrates.
During the digestion process, starch is partially transformed into maltose by salivary or pancreatic enzymes, called amylases; Maltase is secreted by the intestine and then converts maltose into glucose. The body either uses the glucose or stores it as glycogen, also known as animal starch, in the liver.
Six intestinal enzymes are needed for starch digestion, two of which are luminal endo-glucosidases, also known as alpha-amylases. The remaining four enzymes have been identified as various maltases, exo-glucosidases bound to the enterocytes' luminal surface. The sucrase-isomaltase system was linked to two of these maltase activities (maltase Ib, maltase Ia). The rest of the two maltases with no distinguishing characteristics were named maltase-glucoamylase (also called maltases II and III). Since they all digest linear starch oligosaccharides to glucose, these four maltases are also known as alpha-glucosidase.
It is similar to alpha-glucosidase in several ways, but the term "maltase" emphasizes the disaccharide nature of the substrate, where the glucose is cleaved, whereas "alpha-glucosidase" emphasizes the bond, whether the substrate is polysaccharide or disaccharide.
Vampire bats are said as the only vertebrates, which are known to not exhibit intestinal maltase activity.
Maltase is a member of the GH13 (Glycoside hydrolase family 13) of intestinal enzymes that are responsible for transforming complex carbohydrates' - glucosidase linkages into simple glucose molecules for usage. Then, these glucose molecules would be used as a sort of "food" for cells to produce the energy (it means, Adenosine triphosphate) during Cellular respiration. The genes that can code for maltase are given below:
Acid alpha-glucosidase that is coded on the GAA gene is required to break down complex sugars known as Glycogen into glucose.
Maltase-glucoamylase, coded on the MGAM gene, plays a vital role in the digestion of starches. This is because of this enzyme in humans that starches of plant origin are able to digest.
Sucrase-isomaltase, coded on the SI gene, is required for the digestion of carbohydrates, including sucrose, isomaltose, and starch.
Alpha-amylase 1, which is encoded by the AMY1A gene, is responsible for cleaving -glucosidase linkages in polysaccharides and oligosaccharides to generate glycogen and starches, which are then catalyzed by the previous enzymes. This gene's higher quantities in the brain have been represented to lower the risk of Alzheimer's disease.
The hydrolysis of alpha-glucosidase linkage is the mechanism of all Family GH13 enzymes. Maltase focuses on dissolving maltose, which is a disaccharide with a -(1->4) bond connecting two units of glucose. The substrate size determines the rate of hydrolysis (or the carbohydrate size).
Acid Maltase Deficiency (AMD), also called Pompe disease, was first described in 1932 by a Dutch pathologist named JC Pompe. AMD is given as a non-sex-linked autosomal recessive condition, where the excessive accumulation of glycogen builds up within the lysosome vacuoles in nearly all types of cells and all over the body. It is the most serious glycogen storage disease that affects muscle tissue.
AMD is also categorized into three separate types according to the age of onset of the symptoms in affected individuals. Infantile (which is Type a), childhood (which is Type b), and adulthood (which is Type c). The AMD type is defined by the gene mutation type, which was localized in 17q23. At the same time, the mutation type will determine the production level of acid maltase. AMD is fatal, and type-a generally dies of heart failure before age one. Type-b die of respiratory failure between 3-24 ages. And, type-c die of respiratory failure at the age of 10-20 of the onset of symptoms.
Production of Maltase Enzyme
Starch is partially transformed into maltose during the digestion process by the salivary or pancreatic enzymes known as amylases (amylase maltase); maltase is secreted by the intestine and then converts maltose into glucose. The so-produced glucose is either utilized by the body or can be stored in the liver as glycogen (or called animal starch).
Alpha-amylase contains an essential function in the degradation of starches, so it is extremely and commonly used in the baking industry of baking. Also, it is mostly used as a means of flavor, enhancing it to improve bread quality. With no alpha-amylase, the yeast would not be possible to ferment.
Commonly, maltose-glucoamylase can be used as a fermentation source as it is capable of cutting starch into maltose that can then be used for brewing sake and beers.
Maltose glucoamylase has been studied outside of brewing by adding complex inhibitors to avoid the hydrolysis of alpha-glucosidase linkages. By inhibiting the linkage cleave, scientists are hoping to devise a drug that is less toxic and more efficient to treat diabetes.
Amino Acids in Maltase
We have learned already that maltase is a very important part of our body mechanism and plays a vital role in it. We have also seen what deficiency of maltase can cause and how it helps in the process of conversion of maltose into glucose. Now let’s understand which amino acids are present in maltase. Studies have shown that tryptophan, histidine, and cysteine are required for both maltase and glucoamylase activities in the kidney enzyme, whereas tryptophan, histidine, and lysine were required for maltase and glucoamylase activities in the intestine enzyme.
Maltase Use in Yeast and its Mechanism
Maltase is a part of our daily life but also it has many daily life applications one of which is bread. Interestingly, the enzyme maltase, which converts maltose to glucose, is present in the yeast which is used in bread-making. Now let’s understand the mechanism of how maltase helps yeast in the making of bread. A maltose molecule is first absorbed by the yeast cell and maltase then binds it to maltose, splitting it into two or half. Invertase, like sucrose, is a sucrose-breaking enzyme that is also found in yeast cells. This enzyme works on the flour's small amount of sucrose. These two enzymes invertase and maltase which are responsible for creating a large portion of the glucose required for yeast to ferment and form the final product which is bread.
Effect of pH on Enzymes
In chemistry pH is a key term that is commonly heard either it’s experimenting in labs or going through theories, similarly the pH is also connected to enzymes as enzymes are also affected by the changes in the pH level. Many things can be scaled on the basis of pH in chemistry, similarly determining what will be the right pH helps a lot in the case of enzymes too. In this case, the most favorable pH value helps in determining the point at which the enzyme is most active and this point is also known as the optimum pH.
The extreme level of high or low pH values sometimes results in a complete loss of activity in most of the enzymes. pH is also a key factor in maintaining the stability of enzymes. As with the activity, for each of the enzymes, there is also a region of pH optimal stability.
Enzymes their Substrates and the End-products
There are many other enzymes along with maltase that play a vital role in the digestion process in the human body as well as in other processes but in which they form their substrate and an end product. Let's have a look at a few enzymes including maltase with their substrate and end products.
Maltase- The substrate of maltase is maltose which when carried further in the process gives glucose as the final product or end product.
Protease- Protease is an enzyme that is produced in the stomach and pancreas. The substrate of protease is protein and the end product is amino acids.
Lipase- Lipase is produced in the pancreas; its substrate is lipids which in simple language can also be said as fats and oils for the main end product which are fatty acids and glycerol.
Pancreatic amylase- The substrate of pancreatic amylase is starch which finally forms maltose as its final product and is also produced in the pancreas.
Salivary amylase- Salivary amylase is produced in the salivary glands as can be understood by the name itself; its substrate is starch and the end product is maltose.