Enzyme Technology Problems on “Recent Advances – Glucosidases Used in Synthetic Reaction”.
1. Use of glycosidases in synthetic reactions is a comparatively neglected topic.
A. True
B. False
Answer: A
Clarification: Use of glycosidases in synthetic reactions is comparatively neglected topic because of the following reasons:
• Polysaccharides can be obtained readily from plant or microbial sources.
• Polysaccharide function is not so specifically related to its structure.
• The theory describing the functional significance of oligosaccharides is still being developed.
• As there is an abundance of knowledge about glycosidases and their specificities, there is no fundamental reason why they should not be used to synthesize oligosaccharides.
Hence the above statement is true.
2. Which of the following enzyme is not used to construct oligosaccharides?
A. Dextransucrase
B. Levansucrase
C. Papain
D. Cyclomaltodextrin glucanotransferase
Answer: C
Clarification: The enzymes used to construct oligosaccharides such as glucose, fructose or galactose residues are dextransucrase, levansucrase, cyclomaltodextrin glucanotransferase and β-galactosidase. Papain is a protease obtained from papaya and is used in meat tenderization.
3. Which of the following compounds are synthesized by fructosyltransferases?
A. Sucrose-6-acetate
B. Xylosucrose
C. L-aspartate
D. Neosugar
Answer: C
Clarification: Fructosyltransferases are used to synthesize compounds such as sucrose-6-acetate, xylosucrose and the low cariogenic sweetener, ‘neosugar’. L-aspartate is produced from L-aspargine using asparginase enzyme.
4. ____________ is a low cariogenic sweetener, which consists of a mixture of glucose, sucrose and β-2,1 linked fructans with terminal non-reducing glucose residues.
A. Neosugar
B. Xylosucrose
C. Lactose
D. Sucrose
Answer: A
Clarification: Neosugar is a low cariogenic sweetener, which consists of a mixture of glucose, sucrose and β-2,1 linked fructans with terminal non-reducing glucose residues. Xylosucrose is β-D-fructofuranose-(2,1)-a-D-xylopyranoside which is synthesized by fructosyltransferases. Lactose is a disaccharide made up of glucose and galactose. Sucrose is also a disaccharide made up of glucose and fructose.
5. _____________is used to produce dextran from sucrose.
A. Fructosyltransferases
B. Dextransucrase
C. Papain
D. Streptokinase
Answer: B
Clarification: Dextran which is a polymer of a-1,6 linked glucose residues, is produced from sucrose using dextransucrase. Fructosyltransferases are used to synthesize compounds such as sucrose-6-acetate, xylosucrose and neosugar’. Papain is a protease obtained from papaya and is used in meat tenderization. Streptokinase is used in the treatment of blood clots and it converts plasminogen to plasmin.
6. ___________ synthesizes N-acetyllactosamine using a carbon-celite column to remove it, as soon as it is formed.
A. Dextransucrase
B. Streptokinase
C. β – galactosidase
D. Ribonuclease
Answer: C
Clarification: N-acetyllactosamine is a β-D-galactopyranosyl-(1,6)-2-acetamido-2-deoxy-D-glucose which is synthesized by using β – galactosidase using a carbon-celite column to remove it, as soon as it is formed. Dextransucrase is used to produce dextran from sucrose. Streptokinase is used in the treatment of blood clots and it converts plasminogen to plasmin. Ribonuclease has an antiviral activity that acts by hydrolyzing RNA.
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