TRANSAMINATION OF AMINO ACIDS
(Two amino acids can be directly deaminated: Serine and Threonine. They do not undergo this process of transamination.)
Schiff base linkages
These occur frequently in metabolic reactions. Some examples:
(1) Glycolysis - in the mechanism of aldolase
(2) Phosphogluconate pathway - in the mechanism of transaldolase
(3) Amino acid degradation - with PLP in transamination reactions
A Schiff base linkage is a covalent linkage, involving imine formation between a free amino group and a carbonyl group (from, e.g. an aldehyde or ketone).
Mechanism of transamination
PLP plays a central role here in the interconversion of an amino acid and an alpha-keto acid.
(1) Transaminase binds pyridoxal phosphate in a Schiff-base link to a Lysine residue of enzyme (the attachment is to the epsilon-amino group of the Lysine). This forms an "aldimine".
(2) As a new substrate substrate enters the active site, its amino group displaces the -NH2 of active site Lysine. Then a new Schiff-base link is formed to the alpha-amino group of the substrate, as the active site Lysine moves aside.
(3) There is an electronic rearrangement resulting in shifting the double bond to form a "ketimine".
(4) This is followed by hydrolysis to release PMP and an alpha-keto acid.
(5) PMP combines with alpha-ketoglutarate in a reversal of steps 1-4. The net result is transfer of an amino group to alpha-ketoglutarate, and release of glutamate, while regenerating the PLP-enzyme complex.
together with this, I've included a utube link,( https://www.youtube.com/watch?v=l0V-Xmps1mE)
so you guys can have a look and get the picture how it goes =) happy studying!!
from, I LOVE BIOCHEM