Characterizing a proposed novel enzyme family of reversible hydroxyarylic acid decarboxylases

Abstract

In this research, two adjacent genes, shdC and shdD, were found necessary to encode an active 4-hydroxybenzoate decarboxylase (ShdCD) from Sedimentibacter hydroxybenzoicus JW/Z-1 (formerly Clostridium hydroxybenzoicum JW/Z-1). Homology searches of ShdCD revealed three homologues with the same genetic arrangement - the homologues to shdC and shdD adjacent to each other. These homologues are from Streptomyces sp.D7, Bacillus subtilis, and Escherichia coli O157:H7. The homologue from Streptomyces sp.D7 had already been identified as a vanillate decarboxylase in the laboratory of Dr. Julian Davies. The genes encoding the three homologues were cloned into E. coli JM109, expressed, and assayed for decarboxylase activity. The homologues from Streptomyces sp.D7 and B. subtilis are vanillate decarboxylases, and the one from E. coli O157:H7 is a 4-hydroxybenzoate decarboxylase. Based on sequences and enzyme activities, we propose that the decarboxylases from S. hydroxybenzoicus, B. subtilis, Streptomyces sp.D7, and E. coli O157:H7 represent a novel enzyme family.