Question

A non- proteinaceous enzyme is
(a) Ligase
(b) Deoxyribonuclease
(c) Lysozyme
(d) Ribozyme

Answer 1

Hint: Enzymes are molecules that facilitate reactions in a living cell without undergoing too much change i.e. these are biological catalysts and they are almost a protein. Other biological macromolecules like sugars and fats are less suited for such a function. But there are certain molecules that catalyze chemical reactions in a similar way to that of protein enzymes. They are termed as non- proteinaceous enzymes.

Complete step by step answer:
Ribozymes are the catalytic or autocatalytic RNA molecules with sequence- specific cleavage activity. They act as RNA cutting enzymes and are detected in viruses, plants, and animals. Enzymes are exceedingly efficient catalytic biomolecules with controllable activity. They serve as regulators of metabolism, selectively accelerate the approach of biochemical reactions to equilibrium, and increase the efficiency of energy transactions. Ligases are proteinaceous enzymes which catalyze the condensation polymerization of molecules through covalent bonding, accompanied by the cleavage of an energy bond of ATP. Lysozyme is a naturally occurring enzyme found in bodily secretions such as tears, saliva, and milk. It functions as an antimicrobial agent by cleaving the peptidoglycan component of bacterial cell walls, which leads to cell death. A Deoxyribonuclease (DNase, for short) is an enzyme that catalyzes the hydrolytic cleavage of phosphodiester linkages in the DNA backbone, thus degrading DNA. The catalytic property of RNA was first reported by Sydney Altman, Thomas Cech, Zaug, and Grabowski. The discovery that a non- protein macromolecule can serve as a biological catalyst was a marked deviation from the prevailing concept that all enzymes are protein. Self- splicing rRNAs and ribonuclease P are examples of ribozymes. There are two categories of ribozymes; self- splicing ribozymes and self- cleaving ribozymes.
So, the answer is 'Ribozyme'

Additional Information:
- Enzymes are less stable and thermolabile molecules. So they can be easily inhibited, inactivated, or destroyed by high temperature, pH, UV rays, etc.
- Enzymes do not alter the thermodynamic properties of the reactions but only alter the kinetic properties.
- Enzymes catalyze the energetically feasible reactions.
- Enzymes can catalyze a broad spectrum of reactions.

Note:
- The catalytic property of proteinaceous enzymes depends upon their intact organization.
- If an enzyme is denatured or degraded its catalytic ability gets lost. It is estimated that there are about 10⁴ enzyme molecules, capable of catalyzing nearly 2000 odd kinds of reactions.
- The fundamental reactions which ribozymes catalyze are transesterification and sequence- specific cleavage or hydrolysis of phosphodiester bonds for splitting RNA molecules.