Publications

• Characterization and sequence of Escherichia coli pabC, the gene encoding aminodeoxychorismate lyase, a pyridoxal phosphate-containing enzyme.

  Green J.M., Merkel W.K., Nichols B.P.

  In Escherichia coli, p-aminobenzoate (PABA) is synthesized from chorismate and glutamine in two steps. Aminodeoxychorismate synthase components I and II, encoded by pabB and pabA, respectively, convert chorismate and glutamine to 4-amino-4-deoxychorismate (ADC) and glutamate, respectively. ADC lya ... >> More

  In Escherichia coli, p-aminobenzoate (PABA) is synthesized from chorismate and glutamine in two steps. Aminodeoxychorismate synthase components I and II, encoded by pabB and pabA, respectively, convert chorismate and glutamine to 4-amino-4-deoxychorismate (ADC) and glutamate, respectively. ADC lyase, encoded by pabC, converts ADC to PABA and pyruvate. We reported that pabC had been cloned and mapped to 25 min on the E. coli chromosome (J. M. Green and B. P. Nichols, J. Biol. Chem. 266:12971-12975, 1991). Here we report the nucleotide sequence of pabC, including a portion of a sequence of a downstream open reading frame that may be cotranscribed with pabC. A disruption of pabC was constructed and transferred to the chromosome, and the pabC mutant strain required PABA for growth. The deduced amino acid sequence of ADC lyase is similar to those of Bacillus subtilis PabC and a number of amino acid transaminases. Aminodeoxychorismate lyase purified from a strain harboring an overproducing plasmid was shown to contain pyridoxal phosphate as a cofactor. This finding explains the similarity to the transaminases, which also contain pyridoxal phosphate. Expression studies revealed the size of the pabC gene product to be approximately 30 kDa, in agreement with that predicted by the nucleotide sequence data and approximately half the native molecular mass, suggesting that the native enzyme is dimeric. << Less

  J. Bacteriol. 174:5317-5323(1992) [PubMed] [EuropePMC]

• Three-dimensional structure of 4-amino-4-deoxychorismate lyase from Escherichia coli.

  Nakai T., Mizutani H., Miyahara I., Hirotsu K., Takeda S., Jhee K.-H., Yoshimura T., Esaki N.

  4-Amino-4-deoxychorismate lyase (ADCL) is a member of the fold-type IV of PLP dependent enzymes that converts 4-amino-4-deoxychorismate (ADC) to p-aminobenzoate and pyruvate. The crystal structure of ADCL from Escherichia coli has been solved using MIR phases in combination with density modificati ... >> More

  4-Amino-4-deoxychorismate lyase (ADCL) is a member of the fold-type IV of PLP dependent enzymes that converts 4-amino-4-deoxychorismate (ADC) to p-aminobenzoate and pyruvate. The crystal structure of ADCL from Escherichia coli has been solved using MIR phases in combination with density modification. The structure has been refined to an R-factor of 20.6% at 2.2 A resolution. The enzyme is a homo dimer with a crystallographic twofold axis, and the polypeptide chain is folded into small and large domains with an interdomain loop. The coenzyme, pyridoxal 5'-phosphate, resides at the domain interface, its re-face facing toward the protein. Although the main chain folding of the active site is homologous to those of D-amino acid and L-branched-chain amino acid aminotransferases, no residues in the active site are conserved among them except for Arg59, Lys159, and Glu193, which directly interact with the coenzyme and play critical roles in the catalytic functions. ADC was modeled into the active site of the unliganded enzyme on the basis of the X-ray structures of the unliganded and liganded forms in the D-amino acid and L-branched-chain amino acid aminotransferases. According to this model, the carboxylates of ADC are recognized by Asn256, Arg107, and Lys97, and the cyclohexadiene moiety makes van der Waals contact with the side chain of Leu258. ADC forms a Schiff base with PLP to release the catalytic residue Lys159, which forms a hydrogen bond with Thr38. The neutral amino group of Lys159 eliminates the a-proton of ADC to give a quinonoid intermediate to release a pyruvate in accord with the proton transfer from Thr38 to the olefin moiety of ADC. << Less

  J. Biochem. 128:29-38(2000) [PubMed] [EuropePMC]