Which of the following enzymes is not of protein origin?

• a) Hexokinase
• b) Synthetase
• c) Endonuclease
• d) Ribozyme

Among the options provided, the enzyme that is not of protein origin is d) Ribozyme.

Understanding Enzyme Types

Enzymes are biological catalysts that speed up chemical reactions in living organisms. They can be classified based on their composition:

• Protein Enzymes: Most enzymes, like hexokinase, synthetase, and endonuclease, are made of proteins.
• Ribozymes: These are unique because they are made of RNA and can catalyze reactions, distinguishing them from typical protein enzymes.

Examples of Each Type

Here’s a brief overview of the enzymes mentioned:

• Hexokinase: A protein enzyme that helps in glucose metabolism.
• Synthetase: Another protein enzyme involved in synthesizing molecules.
• Endonuclease: A protein enzyme that cuts DNA or RNA strands.
• Ribozyme: An RNA molecule that can catalyze specific biochemical reactions.

In summary, ribozymes are the exception here, as they are not proteins but RNA-based catalysts.