Question

Which of the following enzymes cleaves polysaccharide chains and yields maltose exclusively? (A) \(a\) -Amylase (B) \( \beta\) -Amylase (C) Debranching enzyme (D) Glycogen phosphorylase

Short answer

(B) \( \text{β-Amylase} \)

Step-by-step solution

Identify the Enzyme Functions

Consider the function of each enzyme option. (a) \( \text{α-Amylase} \) - Breaks down starch into smaller carbohydrates but does not yield maltose exclusively.(b) \( \text{β-Amylase} \) - Cleaves polysaccharide chains and produces maltose exclusively.(c) \( \text{Debranching enzyme} \) - Removes branch points in glycogen or amylopectin.(d) \( \text{Glycogen phosphorylase} \) - Cleaves glucose units from glycogen but does not produce maltose.

Select the Correct Enzyme

From the identified functions, \( \text{β-Amylase} \) is the enzyme that specifically cleaves polysaccharide chains and yields maltose exclusively.

Key concepts

Alpha-Amylase

Alpha-Amylase, often abbreviated as \( \text{α-Amylase} \), plays a crucial role in breaking down starches. It is an enzyme found in both plants and animals, including humans. This enzyme acts on the \( \text{α-1,4-glycosidic} \) bonds in starches, converting them into smaller carbohydrate units like maltose and dextrins. However, it does not exclusively produce maltose.

If you think about how starch is broken down during digestion, \( \text{α-Amylase} \) is the first step. It's present in saliva and pancreatic juice. As you chew, \( \text{α-Amylase} \) begins the process of starch breakdown. Once the food reaches your small intestine, pancreatic \( \text{α-Amylase} \) continues this digestive process. While important, it doesn't produce maltose exclusively but a mix of sugars.

Beta-Amylase

Beta-Amylase, or \( \text{β-Amylase} \), is the star when it comes to producing maltose. This enzyme specifically targets and cleaves the \( \text{α-1,4-glycosidic} \) bonds in polysaccharide chains, but it does so in a way that results only in maltose units.

Beta-Amylase is commonly found in plant seeds and sweet potatoes. By breaking down chains from the non-reducing ends, \( \text{β-Amylase} \) releases one maltose unit after another. Hence, \( \text{β-Amylase} \) is the enzyme that exclusively yields maltose. This exclusivity makes it unique among the carbohydrates-cleaving enzymes and is the correct answer in the given exercise.

Debranching Enzyme

The Debranching Enzyme has a vital role in the metabolism of glycogen and starch. Unlike \( \text{α-Amylase} \) and \( \text{β-Amylase} \), which act on linear chains, the Debranching Enzyme tackles the complex branched structures.

Specifically, this enzyme deals with branch points found in glycogen (in animals) and amylopectin (in plants). It achieves this by hydrolyzing \( \text{α-1,6-glycosidic} \) bonds, the connect points of branches. This action allows other enzymes to further breakdown the polysaccharide chains without obstruction.

One key point to remember is that the Debranching Enzyme doesn't yield maltose exclusively. Its primary function is to clear branches, facilitating the work of other enzymes.

Glycogen Phosphorylase

Glycogen Phosphorylase plays a key role in glycogen metabolism. This enzyme is crucial for releasing glucose units from glycogen stores in the body. However, unlike \( \text{β-Amylase} \), it doesn't produce maltose.

Glycogen Phosphorylase specifically catalyzes the breaking of \( \text{α-1,4-glycosidic} \) bonds through a process called phosphorolysis. This process releases glucose-1-phosphate from the non-reducing ends of glycogen.

This glucose-1-phosphate can then be converted into glucose-6-phosphate, which can enter glycolysis to be used for energy production. It is an essential metabolic enzyme, especially during periods of fasting when the body needs to mobilize stored energy.