Question

In the function of an aminotransferase enzyme, what ensures that the resulting pyridoxamine phosphate stays inside the active site after the deamination of the first substrate?

A) Covalent bonds with the enzyme.
B) Electrostatic interactions.
C) Hydrophobic interactions.
D) Temporary binding facilitated by a cofactor.

To prevent lysine bound to pyridoxal phosphate (internal aldimine) from losing a proton and becoming a quinonoid intermediate, what stabilizing factor is likely involved?

A) Presence of a metal cofactor.
B) Intramolecular hydrogen bonding.
C) pH-dependent interactions.
D) Conformational changes in the enzyme.

Answer 1

Electrostatic interactions and covalent bonds ensure that pyridoxamine phosphate stays inside the active site, while intramolecular hydrogen bonding stabilizes lysine to prevent the loss of a proton.

Step-by-step explanation:

The resulting pyridoxamine phosphate stays inside the active site after the deamination of the first substrate due to electrostatic interactions. These interactions involve the attraction or repulsion between charged atoms or groups. The positively charged pyridoxamine phosphate is attracted to the negatively charged residues in the active site, which helps to keep it in place. Additionally, the covalent bonding of the pyridoxamine phosphate with the enzyme further ensures that it stays inside the active site.

To prevent lysine bound to pyridoxal phosphate (internal aldimine) from losing a proton and becoming a quinonoid intermediate, intramolecular hydrogen bonding is likely involved.

Hydrogen bonds can stabilize the structure of molecules and prevent certain chemical reactions from occurring. In this case, hydrogen bonds formed within the lysine-pyridoxal phosphate complex help stabilize the lysine and prevent the loss of a proton.