Brain 4-aminobutyrate aminotransferase. Isolation and sequence of a cDNA encoding the enzyme

4-Aminobutyrate aminotransferase is a key enzyme of the 4-aminobutyric acid shunt. It is responsible for the conversion of the neurotransmitter 4-aminobutyrate to succinic semialdehyde. By using oligonucleotide probes based on partial amino acid sequence data for the pig brain enzyme, several overlapping cDNA clones of 2.0-2.2 kilobases in length have been isolated. The largest cDNA clone was selected for sequence analysis. The amino acid sequence predicted from the cDNA sequence shows that the precursor of 4-aminobutyrate aminotransferase consists of the mature enzyme of 473 amino acid residues and an amino-terminal segment of 27 amino acids attributed to the signal peptide. The cofactor pyridoxal-5-P is bound to lysine residue 330 of the deduced amino acid sequence of the mature enzyme.