Structure and function of glutamyl-tRNA reductase involved in 5-aminolaevulinic acid formation.

In most bacteria, in archaea and in plants, the general precursor of all tetrapyrroles, 5-aminolaevulinic acid, is formed by two enzymes. The initial substrate, glutamyl-tRNA, is reduced by NADPH-dependent glutamyl-tRNA reductase to form glutamate 1-semialdehyde. The aldehyde is subsequently transaminated by glutamate-1-semialdehyde 2,1-aminomutase to yield 5-aminolaevulinic acid. The enzymic mechanism and the solved crystal structure of Methanopyrrus kandleri glutamyl-tRNA reductase are described. A pathway for metabolic channelling of the reactive aldehyde between glutamyl-tRNA reductase and the aminomutase is proposed.