Features and application potential of microbial urethanases

Urethanase (EC 3.5.1.75) can reduce ethyl carbamate (EC), a group 2A carcinogen found in foods and liquor. However, it is not yet commercially available. Urethanase has been detected as an intracellular enzyme from yeast, filamentous fungi, and bacteria. Based on the most recent progress in the sequence analysis of this enzyme, it was observed that amidase-type enzyme can degrade EC. All five enzymes had highly conserved sequences of amidase signature family, and their molecular masses were in the range of 52-62 kDa. The enzymes of Candida parapsilosis and Aspergillus oryzae formed a homotetramer, and that of Rhodococcus equi strain TB-60 existed as a monomer. Most urethanases exhibited amidase activity, and those of C. parapsilosis and A. oryzae also demonstrated high activity against acrylamide, which is a group 2A carcinogen. It was recently reported that urease and esterase also exhibited urethanase activity. Although research on the enzymatic degradation of EC has been very limited, recently some sequences of EC-degrading enzyme have been elucidated, and it is anticipated that new enzymes would be developed and applied into practical use. KEY POINTS: • Recently, some urethanase sequences have been elucidated • The amino acid residues that formed the catalytic triad were conserved • Urethanase shows amidase activity and can also degrade acrylamide.