Enzyme Technology Multiple Choice Questions on “Immobilized Enzymes – Production of Amino Acids”.
1. Immobilized __________ was used to resolve racemic mixtures of aminoacids.
A. hydantoinase
B. aspartase
C. histidase
D. aminoacyclase
Answer: D
Clarification: Racemic mixtures of aminoacids may be resolved by using immobilized aminoacyclases. Hydantoinase produces is specific to D-hydantoins which help in production aminoacids by forming D-carbamoyl aminoacids as an intermediate. Aspartase is used to produce aspartic acid from fumaric acid. Histidase used in the production from L-histidine from Achromobacter liquidum.
2. Which enzyme helps in the production of D-aminoacids?
A. Aminoacyclase
B. Invertase
C. Hydantoinase
D. Raffinase
Answer: C
Clarification: Hydantoinase is isolated from Pseudomonas striata. This enzyme is specific to D-hydantoins, which allows specific hydrolysis to D-carbamoyl amino acids which can then be converted to the D-amino acids by chemical treatment with nitrous acid and the remaining L-hydantoin may be simply racemized by base and the process repeated. Aminoacyclase produces L-aminoacids. Invertase is used to produce glucose syrups and raffinase is used in the production of soya milk.
3. D-aminoacids are used in the production of _________
A. glucose syrups
B. low calorific sweetener
C. insecticides
D. sunscreen agents
Answer: C
Clarification: D-aminoacids are produced by enzyme hydantoinase from Pseudomonas striata. These are used in the production of antibiotics and insecticides. Glucose syrups can be produced with the help of enzyme invertase. Aspartase is used in the production of L-aspartic acid which is used a low calorific sweetener. Urocanic acid is a sun-screening agent which may be produced from L-histidine by histidase from Achromobacter liquidum.
4. What does ‘Y’ represent in the following reaction?
Fumaric acid + NH4+ (underset{x}{rightleftharpoons}) L-aspartic acid
A. Invertase
B. Histidase
C. Aspartase
D. Raffinase
Answer: A
Clarification: In the above reaction, ‘Y’ represents aspartase. Aspartase from Escherichia coli converts fumaric acid to L-aspartic acid. L-Aspartic acid is widely used in the food and pharmaceutical industries. Invertase is produced from yeast, whereas raffinase from Mortierella vinacea. Histidase is produced from Achromobacter liquidum.
5. L-aspartic acid is used in _________ industry.
A. cheese making
B. food
C. dairy
D. sucrose
Answer: B
Clarification: L-aspartic acid is produced from aspartase enzyme by acting fumaric acid and ammonia. These are applicable in food and pharmaceutical industry as low calorific sweetener aspartame. Rennet is used in cheese making industry. Lactases are used in the dairy industry. Invertase and raffinase are used in sucrose industry.
6. Immobilized __________ is prepared by entrapping Escherichia coli cells in a k-carageenan gel cross-linked with glutaraldehyde and hexamethylenediamine.
A. raffinase
B. lactase
C. aspartase
D. aminoacyclase
Answer: C
Clarification: Immobilized aspartase is prepared by entrapping Escherichia coli cells in a k – carageenan gel cross-linked with glutaraldehyde and hexamethylenediamine. Immobilized raffinase is prepared by stirring Mortierella vinacea with the sugar beet juice in a batch stirred tank reactors. Yeast lactase are immobilized by incorporation into cellulose triacetate fibers in batch-wise stirred tank reactors. Aminoacyclase is immobilised by adsorption to anion exchange resins and has an operational half-life of about 65 days at 50°C in PBRs with residence times of about 30 min.
7. A crude immobilized-enzyme preparation consisting of heat -treated achromobacter liquidum cells entrapped in a polyacrylamide gel has been used to convert L-histidine to urocanic acid effectively.
A. True
B. False
Answer: A
Clarification: Urocanic acid may be produced from L-histidine by histidase from achromobacter liquidum. The organism has urocanate hydratase activity, which removes the urocanic acid. Hence this organism cannot be used directly used. To overcome this, a brief heat treatment (70°C, 30 min) inactivates this unwanted activity but has little effect on the histidases. Hence immobilized-enzyme preparation consisting of heat – treated achromobacter liquidum cells entrapped in a polyacrylamide gel. Thus, the above statement is true.
8. Hydantoinase and a carbamoylase used in the production of aminoacids from D-hydantoins may be obtained from _____________ species.
A. yeast
B. escherichia
C. aspergillus
D. arthrobacter
Answer: D
Clarification: Hydantoinase and a carbamoylase used in the production of aminoacids from D-hydantoins may be obtained from Arthrobacter species. Yeast species helps in the production of invertase. Aspartase is from Escherichia species whereas lactase can be produced from aspergillus species.