Preparation and Characterization of a Bifunctional Aldolase/Kinase Enzyme: A More Efficient Biocatalyst for CC Bond Formation

• Published in: Chemistry : a European journal Vol. 16; no. 13; pp. 4018 - 4030
• Main Authors: Iturrate, Laura, Sánchez-Moreno, Israel, Oroz-Guinea, Isabel, Pérez-Gil, Jesús, García-Junceda, Eduardo
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 06.04.2010; WILEY‐VCH Verlag
• Subjects: Aldehyde-Lyases - chemistry; Aldehyde-Lyases - metabolism; Aldehydes; Aldolase; aldolases; Amino Acid Sequence; Binding Sites; Biocatalysis; Circular Dichroism; Citrobacter freundii; Crystallography, X-Ray; Dichroism; Dihydroxyacetone; Enzymes; fusion enzymes; Kinases; Models, Molecular; Molecular Sequence Data; Parents; Phosphotransferases - chemistry; Phosphotransferases - metabolism; Protein Engineering; Proteins; Staphylococcus - chemistry; Staphylococcus carnosus; Stereoisomerism
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.200903096

A bifunctional aldolase/kinase enzyme named DLF has been constructed by gene fusion through overlap extension. This fusion enzyme consists of monomeric fructose‐1,6‐bisphosphate aldolase (FBPA) from Staphylococcus carnosus and the homodimeric dihydroxyacetone kinase (DHAK) from Citrobacter freundii CECT 4626 with an intervening linker of five amino acid residues. The fusion protein was expressed soluble and retained both kinase and aldolase activities. The secondary structures of the bifunctional enzyme and the parental enzymes were analyzed by circular dichroism (CD) spectroscopy to study the effect of the covalent coupling of the two parent proteins on the structure of the fused enzyme. Because S. carnosus FBPA is a thermostable protein, the effect of the fusion on the thermal stability of the bifunctional enzyme has also been studied. The proximity of the active centers in the fused enzyme promotes a kinetic advantage as the 20‐fold increment in the initial velocity of the overall aldol reaction indicates. Experimental evidence supports that this increase in the reaction rate can be explained in terms of substrate channeling. When one plus one is more than two: An engineered bifunctional enzyme can catalyze aldol addition reactions by using dihydroxyacetone (DHA; see scheme) as an initial ketone donor. This new enzyme is a more affordable, stable, and efficient biocatalyst than the multienzyme system composed of the free parent enzymes.