During protoplast isolation, the plant cell wall degrading enzymes used, belong to the class :

Question

Accepted Answer

The correct option is 3: Cellulases

Protoplast isolation is a technique fundamental to plant tissue culture and genetic engineering, where the primary objective is to obtain a plant cell that has been completely stripped of its rigid, protective cell wall. This resulting wall-less cell is called a protoplast. To achieve this, the cell wall must be systematically dissolved, and the composition of the plant cell wall dictates the necessary enzymes. The main structural component of a plant cell wall is the polysaccharide cellulose, which forms a dense meshwork. Therefore, the enzyme class required to specifically hydrolyze the long polymer chains of cellulose is **Cellulases**. For a high yield of viable protoplasts, this is typically done using an enzyme cocktail that also includes Pectinase, an enzyme that breaks down the pectin that glues the cells together, thereby liberating individual cells for the cellulase to act upon. Without Cellulases, the core structural integrity of the cell wall would remain intact, and the isolation process would fail.

The incorrect option is 1: Nucleases

Nucleases are a class of enzymes specialized in degrading nucleic acids—Deoxyribonucleic Acid (DNA) and Ribonucleic Acid (RNA). They function by hydrolyzing the phosphodiester bonds that link nucleotides together, playing vital roles in DNA replication, repair, and recombination. Crucially, the plant cell wall is composed of complex polysaccharides (cellulose, hemicellulose, pectin), not nucleic acids. Using nucleases would therefore have no effect on the cell wall structure and would, in fact, pose a severe risk to the cell's genetic material, potentially leading to cell death or unusable protoplasts.

The incorrect option is 2: Lipases

Lipases are enzymes whose biological function is the hydrolysis of lipids (fats and oils) into glycerol and fatty acids. Lipids are major components of all cellular membranes, including the plasma membrane, which is the immediate boundary of the protoplast itself. The cell wall is an extracellular layer composed of carbohydrates. If lipases were used for protoplast isolation, they would immediately begin to degrade the cell's vital plasma membrane, causing it to rupture and leading to the complete lysis (destruction) of the cell instead of successfully liberating the protoplast.

The incorrect option is 4: Peroxidases

Peroxidases are oxidoreductase enzymes that catalyze the decomposition of hydrogen peroxide (H2O2). They are heavily involved in various oxidative biological processes, such as defensive mechanisms against pathogens or the synthesis of structural polymers. In the context of the plant cell wall, peroxidases play a role in the formation and cross-linking of lignin, which strengthens the secondary cell wall in specific tissues. They are involved in **building** or modifying the cell wall structure, but they are not hydrolytic enzymes that break down the fundamental cellulose or pectin polymers for the purpose of removing the wall.