Activation
of
Amino
Acids - The first step in translation is the activation of amino acids. The 20 amino acids commonly found in proteins are first screened to eliminate the D isomers. Only the L amino acids take part in protein synthesis. Many of the other common amino acids which are not used in protein synthesis, e.g. citrulline, alanine, β alanine, etc. are also rejected.
The activation of amino acids takes place through their carboxyl groups. Each amino acid is catalysed by its own specific activating enzyme, called aminoacyl tRNA synthetase, to form an aminoacyl adenylate (aaa) (aminoacyl AMP) in the presence of ATP. A high energy acyl bond is formed between the α-phosphate of A TP and the carboxyl group of the amino acid.
