Question

What is the role of PLP in transamination?

Short answer

PLP functions as a coenzyme in all transamination reactions as well as several amino acid decarboxylation, deamination, and racemization processes. The amino group of a particular lysine group of the aminotransferase enzyme creates a Schiff-base connection (internal aldimine) with the aldehyde group of PLP.

Step-by-step solution

Formation of amino acids.

In order to rebuild the active enzyme-PLP Schiff base and liberate the newly created amino acid, the -amino group of the active site Lys residue attacks the amino acid-PLP Schiff base in a transamination process. Each enzyme binds its amino acid-PLP Schiff base adduct for bond cleavage in the proper geometric configuration.

Tautomerism.  

An amino acid-PLP Schiff base is created by the tautomerization of the -keto acid-PMP Schiff base. The -proton of the substrate amino acid generates a resonance-stabilized C carbanion, whose electrons are delocalized to the protonated pyridinium nitrogen atom of the coenzyme.