This set of Enzyme Technology Multiple Choice Questions & Answers (MCQs) focuses on “Future Prospects – Coenzyme Regenerating Systems”.
1. Coenzyme may be immobilised together with the enzyme and regenerated in situ.
a) True
b) False
View Answer
Explanation: Most of the enzymes utilize coenzymes which must be regenerated as each product molecule is formed. But the application coenzymes are severely limited by the high cost of the coenzymes and difficulties in regenerating the coenzyme. The above problems may be overcome by the immobilizing the coenzyme together with the enzyme and regenerating the coenzyme in situ. Hence the above statement is true.
2. Which of the following is not a coenzyme?
a) NADH
b) ATP
c) Synzyme
d) NADPH
View Answer
Explanation: Synzymes are synthetic polymers or oligomers with enzyme-like activities possess two structural entities, a substrate-binding site and a catalytically effective site. Coenzymes are non-protein organic molecules that bind loosely to an enzyme. Examples of coenzymes are NADPH, ATP, NADH, NAD+, NADP+, etc.
3. Which of the following is not true for coenzymes?
a) Coenzymes may be immobilized/regenerated with the use of whole-cell systems
b) Membrane reactors may be used to immobilize the coenzyme
c) They are referred to as artificial enzymes
d) Coenzymes may be derivatized for adequate immobilization and regeneration
View Answer
Explanation: Synzymes are also referred to as artificial enzymes, and not coenzymes. Hence this statement is not true for coenzymes. The statements which are true are as follows:
• Coenzymes may be immobilized/regenerated with the use of whole-cell systems. But, these have lower efficiency and flexibility as compared to immobilised-enzyme systems
• Membrane reactors may be used to immobilize the coenzyme. but the pore size of the reactor must be smaller than the coenzyme diameter, which may be extremely restrictive.
• Coenzymes may be derivatized for adequate immobilization and regeneration. This process activates the coenzymes so that it attaches to the support, but does not interfere with its biological function.
4. Which of the following coenzyme is not derivatized by alkylation of the exocyclic N6-amino nitrogen of the adenine present in it?
a) Papain
b) Coenzyme A
c) NAD+
d) NADP+
View Answer
Explanation: Papain is a protease enzyme which is used in meat tenderization. Coenzymes may be derivatized for adequate immobilization and regeneration which will activate coenzymes so that it attaches to the support and does not interfere with its biological function. Coenzyme derivatization involves the alkylation of the exocyclic N6-amino nitrogen of the adenine moiety present in the coenzymes NAD+, NADP+, NADH, NADPH, ATP and coenzyme A.
5. Which of the following are high molecular weight water-soluble derivatives which are used for derivatization of co-enzymes?
a) Dextrans
b) Exocyclic N6-amino nitrogen
c) Polyethyleneimine
d) Polyethylene glycols
View Answer
Explanation: Coenzyme derivatization involves the alkylation of the exocyclic N6-amino nitrogen of the adenine moiety present in the coenzymes NAD+, NADP+, NADH, NADPH, ATP and coenzyme A. In some applications where membrane reactors it is necessary to retain the coenzyme of sufficient size within the system. Thus, high molecular weight water-soluble derivatives may be used are they cause less diffusional resistance than insoluble coenzyme matrices. In such cases, dextrans, polyethyleneimine and polyethylene glycols are widely used.
6. Which of the following system is not used to derivatize coenzymes?
a) Alkylation of the exocyclic N6-amino nitrogen of the adenine moiety present in the coenzymes
b) High molecular weight water-soluble derivatives
c) Derivative of myoglobin acts as an effective natural ascorbate oxidase
d) Enzymic regeneration
View Answer
Explanation: Derivative of myoglobin acts as an effective natural ascorbate oxidase and is achieved by attaching (Ru(NH3)5)3+ to three surface histidine residues. This is an example of production of synzyme. The following systems are used to derivatize coenzymes:
• Coenzyme derivatization involves the alkylation of the exocyclic N6-amino nitrogen of the adenine moiety present in the coenzymes NAD+, NADP+, NADH, NADPH, ATP and coenzyme A.
• High molecular weight water-soluble derivatives such as dextrans, polyethyleneimine and polyethylene glycols may be used are they cause less diffusional resistance than insoluble coenzyme matrices.
• Enzymic regeneration is advantageous because of its high specificity. Enzymic processes utilizes cheap substrates and readily available enzymes and give non-interfering and easily separated products. Formate dehydrogenase and acetate kinase are the useful examples in present time.
7. Which of the following is an example of regeneration of the derivatized coenzymes by enzymic means?
a) Formate dehydrogenase
b) Exocyclic N6-amino nitrogen of the adenine moiety
c) Dextrans
d) Polyethylene glycol
View Answer
Explanation: The regeneration of the derivatized coenzymes by enzymic means is advantageous because of its high specificity. Enzymic processes utilizes cheap substrates and readily available enzymes. They also give non-interfering and easily separated products. Formate dehydrogenase and acetate kinase are useful examples of this.
8. What is represented in the following diagram?
a) Formate dehydrogenase
b) Exocyclic N6-amino nitrogen of the adenine moiety
c) Dextrans
d) Acetate kinase
View Answer
Explanation: The coenzyme regeneration of ATP by acetate kinase is shown in the diagram. Acetate kinase is an example for regeneration of the derivatized coenzymes by enzymic means. This is an advantageous process because of highly specific nature of enzymes. In this process, cheap substrate such as acetyl phosphate and readily available enzyme acetate kinase is used. This particular process gives non-interfering and easily separated products such as dextran ADP, acetic acid, product AOPO3-2 etc.
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