Preparation of a Soluble Bifunctional Enzyme by Gene Fusion


Within the cellular framework are a number of sequentially operating enzyme systems, in many cases in the form of bi- or even multifunctional proteins each consisting of a single type of polypeptide chain but having two or more catalytic or binding functions. In order to study the properties of an artificial bifunctional enzyme, an in-frame fusion of the structural genes for β-galactosidase (lacZ) and galactokinase (galK) of Escherichia coli was made in vitro. This DNA chimaera was constructed by connecting the 3′-terminus of the lacZ gene to the 5′-terminus of the galK gene. The translated gene product was able to catalyze the sequential reaction normally carried out by the separate native enzymes.

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