PhhC is an essential aminotransferase for aromatic amino acid catabolism in Pseudornonas aeruginosa

Abstract

SUMMARY: The phhC gene of Pseudomonas aeruginosa encodes a protein which is a member of the Family I aminotransferases. At high expression levels in the heterologous Escherichia oli system, PhhC can compensate for the absence of AspC (which functions in L-aspartate biosynthesis) and TyrB (which functions in aromatic biosynthesis). In the native organism, PhhC is essential for catabolism of either L-tyrosine or L-phenylalanine, as demonstrated by gene inactivation. This catabolic function of PhhC is consistent with its inclusion as the distal gene in the inducible phenylalanine hydroxylase operon. The presence of PhhC for catabolism of aromatic amino acids is required in spite of an existing multiplicity of other P. aeruginosa aminotransferases having a similar pattern of broad substrate specificity in vitm. This implies a spatial orientation of PhhC that effectively specializes it for aromatic amino acid catabolism.