Which enzyme catalyzes the interconversion of isomers?
Isomerases catalyze the interconversion of isomeric forms of molecules.
Ref: NCERT Class 11 Biology Chapter 9: Biomolecules Enzymes - Properties Classification and Cofactors
#enzyme catalysis
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PylC enzyme catalyzes
PylC functions as ATP-dependent ligase catalyzing second step of pyrrolysine pathway, condensation of (3R)-3-methyl-D-ornithine with second L-lysine molecule via amide bond formation between ornithine carboxylate and lysine epsilon-amino group, producing N6-((2R,3R)-3-methylornithyl)-lysine. Mechanism employs ATP to activate carboxylate as acyl-adenylate intermediate then nucleophilic attack by lysine amine, similar to glutathione synthesis. PylC structure resembles D-alanine-D-alanine ligase fold. Deletion of pylC accumulates methylornithine and ablates pyrrolysine formation preventing amber suppression and methylamine methyltransferase synthesis in Methanosarcina. This condensation generates pseudopeptide intermediate essential for subsequent oxidation cyclization into pyrrolysine heterocycle.
Ref: NCBI Bookshelf, Ligases: PylC Condensation Reaction in Pyrrolysine Pathway
Which amino acid has an imidazole side chain and plays a role in enzyme catalysis?
Histidine is the accurate answer because it correctly identifies the biological function or role described in this question. In Amino Acids Basics, understanding the specific functions of molecules, enzymes, or structures is fundamental. Histidine fulfills this particular biological role through its specific structural properties, biochemical activity, or physiological mechanism. The other options (Arginine, Lysine, and Proline) serve different biological functions or are associated with other processes, pathways, or structural roles within the cell or organism.
Ref: Lehninger Principles of Biochemistry, Nelson & Cox, 8th Ed., Ch. 3
The key feature of metal ion catalysis is:
The presence of transition metals in the enzyme correctly identifies the characteristic feature or property described in this question. In Enzymes Basics, specific characteristics define and distinguish biological molecules, organisms, or processes from one another. The feature described by The presence of transition metals in the enzyme is a defining property that arises from its unique molecular structure, evolutionary history, or physiological role. The other options (Formation of enzyme-substrate covalent bonds, Hydrolysis of peptide bonds, and Non-specific binding of any substrate) describe characteristics of different entities, represent incorrect properties, or apply to the subject under different conditions.
Ref: Lehninger Principles of Biochemistry, Nelson & Cox, 8th Ed., Ch. 6
The function of binding energy (ΔGB) in enzyme catalysis is:
To stabilize the transition state is the accurate answer because it correctly identifies the biological function or role described in this question. In Enzymes Basics, understanding the specific functions of molecules, enzymes, or structures is fundamental. To stabilize the transition state fulfills this particular biological role through its specific structural properties, biochemical activity, or physiological mechanism. The other options (To increase activation energy, To convert products back into substrates, and To inhibit enzyme activity) serve different biological functions or are associated with other processes, pathways, or structural roles within the cell or organism.
Ref: Lehninger Principles of Biochemistry, Nelson & Cox, 8th Ed., Ch. 6
Which of the following statements about acid-base catalysis is true?
It involves the transfer of protons is the scientifically accurate answer to this question. Within the study of Enzymes Basics, this concept is well-established through extensive research and is documented in standard scientific literature. The specific properties, mechanisms, or characteristics of It involves the transfer of protons directly address what is being asked. Among the other options, It only occurs in the presence of water, It requires metal ions, and It cannot increase reaction rates do not correctly answer this question because they either refer to different concepts, describe properties of other molecules or processes, or represent common misconceptions about this topic.
Ref: Lehninger Principles of Biochemistry, Nelson & Cox, 8th Ed., Ch. 6
Which of the following metal ions is not commonly involved in enzyme catalysis?
Na⺠is the correct choice because it does not accurately describe or belong to the category addressed in this question. In the context of Enzymes Basics, the other options (Cu²âº, Fe²âº, and Mn²âº) are all valid and well-established concepts. Na⺠is either unrelated to the topic, describes a different biological process, or represents a common misconception. Questions framed as 'which is NOT' require students to identify the exception among otherwise correct statements, demanding comprehensive knowledge of the topic rather than recognition of a single fact.
Ref: Lehninger Principles of Biochemistry, Nelson & Cox, 8th Ed., Ch. 6
What is the rate-limiting step in enzyme catalysis?
Transition state formation accurately defines or describes the concept asked in this question. Within Enzymes Basics, precise definitions and terminology are essential for clear scientific communication. The other options (Substrate binding, Product release, and Enzyme conformational change) either describe related but distinct concepts, use incorrect terminology, or confuse similar-sounding terms that have different scientific meanings. A thorough understanding of exact definitions helps distinguish between closely related biological concepts and is crucial for competitive examinations.
Ref: Lehninger Principles of Biochemistry, Nelson & Cox, 8th Ed., Ch. 6