Passage 6 (Questions 30-35)O-GlcNAcylation, the addition of an N-acetyl-glucosamine group (O-GlcNAcyl) to a serine or threonine residue of a protein, has been identified in over 3,000 different proteins. Disruptions of O-GlcNAcylations have been implicated in major health conditions, including diabetes, cancer, and neurodegenerative diseases. The mechanism for O-GlcNAcylation is depicted in Reaction 1, with the forward reaction being catalyzed by O-GlcNAc transferase (OGT) and the reverse reaction by O-GlcNAcase (OGA).Reaction 1Reaction 1Interested in the substrate specificity of OGT, researchers conducted kinetic assays to determine kinetic parameters of OGT against 26 UDP-GlcNAc analogs. Analogs differed from UDP-GlcNAc at C2, C4, and C6 of the glucosamine ring. Figure 1 shows four select analogs.Figure 1 UDP-GlcNAc and select analogsThe results of the study revealed that modifications to the substituents of these carbons are generally not tolerated with roughly 15% of the analogs being recognized and accepted by OGT. The kinetic results of UDP-GlcNAc and the four analogs shown in Figure 1 are shown in Table 1.Table 1 Kinetic Parameters of UDP-GlcNAc and Select Analogs Kinetic Constants UDP-GlcNAc Analog A Analog B Analog C Analog D Km (µM) 8.5 141.8 369 282.1 No activity Vmax (µM/min)1.3 2.8 3.2 3.7 No activity Despite the low recognition rate by OGT, tolerance patterns of UDP-GlcNAc analogs emerged that may indicate the molecular locations of substrate-enzyme interactions. Based on these patterns, researchers suspect the presence and orientation of C4 and C6 hydroxyl groups, as well as the C2 N-acetyl group, play a crucial role in OGT specificity.Adapted from: X. Ma, P. Liu, H. Yan, et al., "Substrate Specificity Provides Insights into the Sugar Donor Recognition Mechanism of O-GlcNAc Transferase (OGT)." PLoS ONE. ©2013 Ma et al.Question 31The non-covalent interactions occurring between N-acetyl-glucosamine functional groups and OGT are most likely:A.hydrogen bonds.B.glycosidic bonds.C.ionic salt bridges.D.hydrophobic interactions.
Question
Passage 6 (Questions 30-35)O-GlcNAcylation, the addition of an N-acetyl-glucosamine group (O-GlcNAcyl) to a serine or threonine residue of a protein, has been identified in over 3,000 different proteins. Disruptions of O-GlcNAcylations have been implicated in major health conditions, including diabetes, cancer, and neurodegenerative diseases. The mechanism for O-GlcNAcylation is depicted in Reaction 1, with the forward reaction being catalyzed by O-GlcNAc transferase (OGT) and the reverse reaction by O-GlcNAcase (OGA).Reaction 1Reaction 1Interested in the substrate specificity of OGT, researchers conducted kinetic assays to determine kinetic parameters of OGT against 26 UDP-GlcNAc analogs. Analogs differed from UDP-GlcNAc at C2, C4, and C6 of the glucosamine ring. Figure 1 shows four select analogs.Figure 1 UDP-GlcNAc and select analogsThe results of the study revealed that modifications to the substituents of these carbons are generally not tolerated with roughly 15% of the analogs being recognized and accepted by OGT. The kinetic results of UDP-GlcNAc and the four analogs shown in Figure 1 are shown in Table 1.Table 1 Kinetic Parameters of UDP-GlcNAc and Select Analogs Kinetic Constants UDP-GlcNAc Analog A Analog B Analog C Analog D Km (µM) 8.5 141.8 369 282.1 No activity Vmax (µM/min)1.3 2.8 3.2 3.7 No activity Despite the low recognition rate by OGT, tolerance patterns of UDP-GlcNAc analogs emerged that may indicate the molecular locations of substrate-enzyme interactions. Based on these patterns, researchers suspect the presence and orientation of C4 and C6 hydroxyl groups, as well as the C2 N-acetyl group, play a crucial role in OGT specificity.Adapted from: X. Ma, P. Liu, H. Yan, et al., "Substrate Specificity Provides Insights into the Sugar Donor Recognition Mechanism of O-GlcNAc Transferase (OGT)." PLoS ONE. ©2013 Ma et al.Question 31The non-covalent interactions occurring between N-acetyl-glucosamine functional groups and OGT are most likely:A.hydrogen bonds.B.glycosidic bonds.C.ionic salt bridges.D.hydrophobic interactions.
Solution
The non-covalent interactions occurring between N-acetyl-glucosamine functional groups and OGT are most likely:
A. hydrogen bonds.
The reasoning behind this is that the passage mentions the importance of the presence and orientation of C4 and C6 hydroxyl groups, as well as the C2 N-acetyl group, in OGT specificity. Hydroxyl groups and N-acetyl groups are polar and can form hydrogen bonds. Glycosidic bonds are covalent bonds that link sugar molecules together, not non-covalent interactions. Ionic salt bridges typically occur between charged groups, and there's no mention of such groups in the passage. Hydrophobic interactions usually involve nonpolar groups, while the groups mentioned in the passage are polar. Therefore, hydrogen bonds are the most likely type of non-covalent interactions occurring between N-acetyl-glucosamine functional groups and OGT.
Similar Questions
Based on Figure 1, a GlcNAc residue in the glycan chain is linked to a mannose residue by:A.a glycosidic bond between carbon 1 of GlcNAc and carbon 4 of mannose.B.a glycosidic bond between carbon 1 of mannose and carbon 4 of GlcNAc.C.a glycosidic bond between carbon 1 of GlcNAc and carbon 3 of mannose.D.a glycosidic bond between carbon 1 of mannose and carbon 3 of GlcNAc.
Which of the following pair of enzymes are involved in the synthesis of glycogen?Group of answer choicesGlycogen synthase and amylo (1→4) to (1→6) transglycosylaseGlycogen synthase and oligo (1→6) to (1→4) glucantransferaseGlycogen phosphorylase and amylo (1→4) to (1→6) transglycosylaseGlycogen phosphorylase and oligo (1→6) to (1→4) glucantransferase
N-acetylcysteine (NAC) is often administered for the treatment of acetaminophen overdose to help prevent the toxic metabolite, NAPQI, from accumulating in hepatocytes. This is most likely because NAC:Question 33 Answer Choices A. increases the production of NAPQI. B. acts as an inhibitor of glutathione reductase. C. acts to stimulate the action of CYP1A2. D. possesses a, sterically unhindered functional group equivalent to glutathione.
Fill in the Blank QuestionFill in the blank question.Glycogenolysis and gluconeogenesis are stimulated by the pancreatic hormone .
What reaction does glycogen synthase catalyse?Group of answer choicesThe hydrolytic cleavage of α (1→4) bondsThe transfer of 6 or 7 glucose molecules to the C-6 hydroxyl group of an internal glucose residue in the glycogen chainThe transfer of a glucose molecule to the nonreducing end of glycogen branchesThe hydrolytic cleavage of α (1→6) bonds
Upgrade your grade with Knowee
Get personalized homework help. Review tough concepts in more detail, or go deeper into your topic by exploring other relevant questions.