NUCLEOTIDE-SEQUENCE OF THE ESCHERICHIA-COLI K-12 TRANSKETOLASE (TKT) GENE

The gene tkt for the enzyme transketolase (TK; EC 2.2.1.1) of Escheric hia coli K-12 was subcloned and the complete DNA sequence was determin ed from both strands. An open reading frame with 1992 bp was detected that could encode a protein with a subunit mass of 72 143. The gene fo rms a monocistronic operon and is transcribed counterclockwise to the E. coli chromosome. From recombinant strains, the enzyme was purified and 39 N-terminal amino acid residues were determined. The DNA-derived protein sequence showed 49.5% identical amino acid residues with the transketolase of Rhodobacter sphaeroides, 46.8% identity with the enzy me from Saccharomyces cerevisiae, and 28.9% identity with the human tr ansketolase.