Indiana University-Purdue University Indianapolis (IUPUI) / Anbu is a bacterial protein with significant homology to the sub-units of the 20S proteasome and is predicted to be a novel bacterial proteasome. The goal of this project was to determine if the recombinant Anbu protein from Pseudomonas aeruginosa is a proteasome. Anbu from P. aeruginosa was successfully cloned, expressed and purified. In order to determine the catalytic activity of Anbu, the purified protein was tested with a variety of substrates and conditions. The targets analyzed included fluorescently-labeled substrates, denatured proteins, diubiquitin, and a peptide library in the hopes of obtaining a useful model substrate. Experiments were also conducted to determine what role Anbu has in the cell. Western analysis was performed on the cell lysate of wild type P. aeruginosa and insertional mutants to detect Anbu expression. The level of biofilm formation was compared between the wild type and mutants. Cultures were grown under stress conditions including the oxidative stress of diamide and the nitrosative stress of S-nitrosoglutathione. Growth rates were monitored in an attempt to detect a phenotypic difference between the wild type and the mutants lacking Anbu, HslV, and the other proteins of interest. While a substrate for Anbu has yet to be found, this protein was found to assemble into a larger structure and P. aeruginosa lacking Anbu was sensitive to the oxidative stress of diamide and the nitrosative stress of S-nitrosoglutathione.