ISOLATING THERMOSTABLE ENZYMES FROM ENGINEERED MESOPHILES

摘要

A thermostable enzyme free from unwanted contaminants is isolated by: (a) providing a mesophilic host cell engineered to express a gene encoding a heterologous thermostable enzyme; (b) culturing the mesophilic host cell and producing the thermostable enzyme in a mixture comprising unwanted contaminants; and (c) purifying the thermostable enzyme by a method that includes heating the enzyme and the unwanted contaminants to a temperature sufficient to inactivate the unwanted contaminants but not sufficient to inactivate the thermostable enzyme. A method of assaying for nucleic acid ligase is described which includes forming an adenyl adduct with the ligase and detecting the adduct. The latter method is used to screen a library of transformants for the ability to express the nucleic acid ligase.