In recent years, growing attention has been devoted to cold adapted microorganisms and their enzymes. A gene library was constructed using the genome of a new aerobic psychrotolerant marine isolate Pseudoalteromonas arctica sp. nov. The gene encoding an esterase was identified by screening the library on tributyrin plates. The recombinant protein was purified (3,3 - fold) in one step using a Ni- column and was subsequently characterised. The enzyme has unique properties since it requires a very low activation energy and retains 50% of its maximal activity at the freezing point of water.