Biochemical studies on a versatile esterase that is most catalytically active with polyaromatic esters

Abstract

Herein, we applied a community genomic approach using a naphthalene‐enriched community (CN 1) to isolate a versatile esterase (CN 1E 1) from the α/β‐hydrolase family. The protein shares low‐to‐medium identity (≤ 57%) with known esterase/lipase‐like proteins. The enzyme is most active at 25–30°C and pH 8.5; it retains approximately 55% of its activity at 4°C and less than 8% at ≥ 55°C, which indicates that it is a cold‐adapted enzyme. CN 1E 1 has a distinct substrate preference compared with other α/β‐hydrolases because it is catalytically most active for hydrolysing polyaromatic hydrocarbon (phenanthrene, anthracene, naphthalene, benzoyl, protocatechuate and phthalate) esters (7200–21 000 units g−1 protein at 40°C and pH 8.0). The enzyme also accepts 44 structurally different common esters with different levels of enantio‐selectivity (1.0–55 000 units g−1 protein), including (±)‐menthyl‐acetate, (±)‐neomenthyl acetate, (±)‐pantolactone, (±)‐methyl‐mandelate, (±)‐methyl‐lactate and (±)‐glycidyl 4‐nitrobenzoate (in that order). The results provide the first biochemical evidence suggesting that such broad‐spectrum esterases may be an ecological advantage for bacteria that mineralize recalcitrant pollutants (including oil refinery products, plasticizers and pesticides) as carbon sources under pollution pressure. They also offer a new tool for the stereo‐assembly (i.e. through ester bonds) of multi‐aromatic molecules with benzene rings that are useful for biology, chemistry and materials sciences for cases in which enzyme methods are not yet available.