4-hydroxybenzoyl-CoA thioesterase (EC 3.1.2.23) is an enzyme from Pseudomonas CBS-3, a soil-dwelling microbe that survives on 4-chlorobenzoate as its sole carbon source. This enzyme [1] catalyzes the last of the three steps in the pathway from 4-chlorobenzoate to hydroxybenzoate, the cleavage of the thioester bond of 4-hydroxybenzoyl-CoA to form hydroxybenzoate.

4-hydroxybenzoyl-CoA thioesterase is a protein of 141 amino-acid residues that assemble as an homotetramer. An aspartate in the N-terminal domain is thought to participate in the catalytic mechanism.

This enzyme is evolutionary related to a number of uncharacterized proteins:

• Escherichia coli hypothetical protein ybgC.
• Aquifex aeolicus hypothetical protein AQ_1494.
• Haemophilus influenzae hypothetical protein HI0386.
• Helicobacter pylori hypothetical protein HP0496.
• Synechocystis strain PCC 6803 hypothetical protein slr0204.
• Synechocystis strain PCC 6803 hypothetical protein sll0410.

We developed a signature pattern based on the region surrounding the potential active site residue.