Enzyme - Glutamyl-tRNA reductase

Alternative Name(s)

There are no alternative names for this Enzyme

Catalytic Activity

(S)-4-amino-5-oxopentanoate + NADP(+) + tRNA(Glu) = H(+) + L-glutamyl-tRNA(Glu) + NADPH


There are no Cofactors for this Enzyme

Reaction Mechanism

    Glutamyl-tRNA Reductase catalyses the reduction of the activated alpha-carboxyl group of glutamate from glutamyl-tRNA using NADPH to form glutamate-1-semialdehyde(GSA). GSA is then converted to 5-aminolevulenic acid, a precursor molecule for the biosynthesis of tetrapyrroles like chlorophylls, hemes and coenzyme B12.

    Cys48 acts as a nucleophile to attack the alpha-carboxyl group of glutamate, which is activated by an ester linkage to tRNA, forming a highly reactive enzyme-localised thioester and tRNA is released. Direct hydride transfer from NADPH, facilitated by His84, which acts as a base catalyst to stabilise the protonated tetrahedral intermediate, leads to the formation of the product GSA.
    Catalytic Residues
    AA Uniprot Uniprot Resid PDB PDB Resid
    Cys Q9UXR8 48 1gpj 48
    His Q9UXR8 84 1gpj 84
    Step Components

    intermediate formation, hydride transfer, enzyme-substrate complex formation, bimolecular nucleophilic addition, overall product formed, native state of enzyme regenerated, enzyme-substrate complex cleavage, overall reactant used, unimolecular elimination by the conjugate base, bimolecular nucleophilic substitution, aromatic unimolecular elimination by the conjugate base

    Step 1.

    The sulfryl group of Cys48 acts as a nucleophile to attack glutamate and the tRNA residue is eliminated. An enzyme thioester intermediate is formed.

    Step 2.

    A hydride is transferred from NADPH to the thioester intermediate. This is promoted by His84.

    Step 3.

    The tetrahedral intermediate collapses, releasing Cys48 and forming the product.


    The products of the reaction.

Reaction Parameters

  • Kinetic Parameters
    Organism KM Value [mM] Substrate Comment
    Escherichia coli 0.039 NADPH pH 8.1, 37°C
  • Temperature

    There are no reaction parameters information for this Enzyme.

  • pH

    There are no reaction parameters information for this Enzyme.

Associated Proteins

Protein name Organism
Glutamyl-tRNA reductase 1, chloroplastic Mouse-ear cress
Probable glutamyl-tRNA reductase 3, chloroplastic Mouse-ear cress
Glutamyl-tRNA reductase 3, chloroplastic Barley
Glutamyl-tRNA reductase 1 Nocardioides sp. (strain ATCC BAA-499 / JS614)
Glutamyl-tRNA reductase 2 Nocardioides sp. (strain ATCC BAA-499 / JS614)