A novel phenol hydroxylase and catechol 2,3-dioxygenase from the thermophilic Bacillus thermoleovorans strain A2: nucleotide sequence and analysis of the genes.

Abstract

The new thermophilic Bacillus thermoleovorans strain A2 degrades phenol and cresols via the meta cleavage pathway. The first two enzymes involved in this process, the phenol hydroxylase and catechol 2,3-dioxygenase, encoded by the pheA and pheB genes respectively, were cloned and sequenced. The deduced amino acid sequence of pheA contains 524 amino acids with a theoretical M(r) of 59,602 Da and displays less than 10% amino acid identity to known phenol hydroxylases. The greatest amino acid identity (54%) displayed by pheA is with the larger component of the two-component 4-hydroxyphenylacetic acid hydroxylase from Escherichia coli W encoded by hpaB. No second component was present on the 3.8-kb insert. The consensus sequence GXGXXG for FAD/NAD binding sites is not present in pheA. PheB encodes a new catechol 2,3-dioxygenase of 308 amino acids (M(r) 35,487 Da) which has greatest amino acid identity (43%) with the 3-methyl catechol 2,3-dioxygenase of Pseudomonas putida UCC2 encoded by tdnC. Both pheA and pheB encode new enzymes which display low sequence homology with those previously published.