Figures & data
Figure 1. Molecular structures of THI (1, 2-acetyl-4-((1R,2S,3R)-1,2,3,4-tetrahydroxybutyl)imidazole), pyridoxal-5′-phosphate (2) and ATP (3).
![Figure 1. Molecular structures of THI (1, 2-acetyl-4-((1R,2S,3R)-1,2,3,4-tetrahydroxybutyl)imidazole), pyridoxal-5′-phosphate (2) and ATP (3).](/cms/asset/e71fc7e5-d30c-4be5-85dc-dbd1f4a3d01b/ienz_a_915396_f0001_b.jpg)
Figure 2. Schematic representation of the pathways describing the interaction of pyridoxal kinase (E) with its two substrates pyridoxal (A) and ATP (B) and their corresponding products pyridoxal-5′-phosphate (P) and ADP (Q).
![Figure 2. Schematic representation of the pathways describing the interaction of pyridoxal kinase (E) with its two substrates pyridoxal (A) and ATP (B) and their corresponding products pyridoxal-5′-phosphate (P) and ADP (Q).](/cms/asset/c581d286-28bc-44f2-bf1f-9bb44c93c2b0/ienz_a_915396_f0002_b.jpg)
Figure 4. Kinetic analysis of pyridoxal kinase inhibition by THI with respect to the cosubstrate ATP shows that THI acts as a non-competitive inhibitor. Lineweaver–Burk (top) and secondary plots (middle, bottom) reveal the inhibition constants Ki = 5.3 mM and Kii = 23.0 mM. Mean values with standard errors are shown from duplicate or triplicate measurements; THI concentrations: • 0 mM, ▪ 4.2 mM, ▴ 7.5 mM, ▾ 15.0 mM and ♦ 20.0 mM.
![Figure 4. Kinetic analysis of pyridoxal kinase inhibition by THI with respect to the cosubstrate ATP shows that THI acts as a non-competitive inhibitor. Lineweaver–Burk (top) and secondary plots (middle, bottom) reveal the inhibition constants Ki = 5.3 mM and Kii = 23.0 mM. Mean values with standard errors are shown from duplicate or triplicate measurements; THI concentrations: • 0 mM, ▪ 4.2 mM, ▴ 7.5 mM, ▾ 15.0 mM and ♦ 20.0 mM.](/cms/asset/97f14e36-160b-4f0b-b569-7a5e4c4c4273/ienz_a_915396_f0004_b.jpg)
Figure 3. Kinetic analysis of pyridoxal kinase inhibition by THI with respect to the substrate pyridoxal (PL) shows that THI acts as a competitive inhibitor. Lineweaver–Burk (top) and secondary plots (middle, bottom) reveal a Kii inhibition constant of 11.2 mM. Mean values with standard errors are shown from duplicate or triplicate measurements; THI concentrations: • 0 mM, ▪ 4.2 mM, ▴ 7.5 mM, ▾ 15.0 mM and ♦ 20.0 mM.
![Figure 3. Kinetic analysis of pyridoxal kinase inhibition by THI with respect to the substrate pyridoxal (PL) shows that THI acts as a competitive inhibitor. Lineweaver–Burk (top) and secondary plots (middle, bottom) reveal a Kii inhibition constant of 11.2 mM. Mean values with standard errors are shown from duplicate or triplicate measurements; THI concentrations: • 0 mM, ▪ 4.2 mM, ▴ 7.5 mM, ▾ 15.0 mM and ♦ 20.0 mM.](/cms/asset/a26eb028-2ac5-4457-8419-d801c350d7ad/ienz_a_915396_f0003_b.jpg)
Figure 5. Schematic overview of competing equilibria describing the inhibition of pyridoxal kinase (E) by THI in the presence of both substrates pyridoxal (PL) and ATP (adapted from Asante-Appiah and ChanCitation34). Ki and Kii refer to the inhibition constants describing a random Bi Bi rapid equilibrium system in which PL and THI compete for the same enzyme binding site.
![Figure 5. Schematic overview of competing equilibria describing the inhibition of pyridoxal kinase (E) by THI in the presence of both substrates pyridoxal (PL) and ATP (adapted from Asante-Appiah and ChanCitation34). Ki and Kii refer to the inhibition constants describing a random Bi Bi rapid equilibrium system in which PL and THI compete for the same enzyme binding site.](/cms/asset/db5da642-300d-47ef-8c07-fb668948be2f/ienz_a_915396_f0005_b.jpg)