Hyperproduction of N-acetylneuraminate lyase by the gene-cloned strain ofEscherichia coli

Microbial aldolases and transketolases: new biocatalytic approaches to simple and complex sugars

Enzymes have become exceedingly valuable tools in organic synthesis as the reactions they catalyze generally proceed under mild conditions and in high stereo- and regioselectivity. Advances in microbiology and genetic engineering have greatly increased the availability of various enzymes. One of the most useful applications of enzyme-catalyzed chemical transformations is in the synthesis of water-soluble, polyfunctional organic molecules such as carbohydrates. As the pivotal roles that carbohydrates play in biological processes become more evident, access to these compounds becomes increasingly important. This review gives a brief overview of the use of aldolases and transketolases in the synthesis of sugars, sugar analogs, and related compounds.

High-level production and purification of Escherichia coli N-acetylneuraminic acid aldolase (EC 4.1.3.3)

The Escherichia coli gene which encodes N-acetylneuraminic acid aldolase was isolated by the polymerase chain reaction, cloned into the inducible expression vector pTTQ18, and overexpressed in E. coli. The high yield of aldolase was achieved through both optimum growth of cells and efficient expression of the aldolase gene (20-30% soluble cellular protein). The recombinant enzyme was purified to homogeneity with an activity of 1.2-2.2 U/mg, which compared favorably with that of commercial preparations of E. coli aldolase (1.1 U/mg) and Clostridium perfringens aldolase (0.4 U/mg). The cloning strategy, fermentation conditions, purification protocol, and activity assay are described.