Analyses of enzyme II gene mutants for sugar transport and heterologous expression of fructokinase gene in Corynebacterium glutamicum ATCC 13032

Corynebacterium glutamicum ATCC 13032 has four enzyme 11 (Ell) genes of the phosphotransferase system in its genome encoding transporters for sucrose, glucose, fructose, and an unidentified Ell. To analyze the function of these Ell genes, they were inactivated via homologous recombination and the resulting mutants characterized for sugar utilization. Whereas the sucrose Ell was the only transport system for sucrose in C. glutamicum, fructose and glucose were each transported by a second transporter in addition to their corresponding Ell. In addition, the ptsF ptsG double mutant carrying deletions in the Ell genes for fructose and glucose accumulated fructose in the culture broth when growing on sucrose. As no fructokinase gene exists in the C glutamicum genome, the fructokinase gene from Clostridium acetobutylieum was expressed in C glutamicum and resulted in the direct phosphorylation of fructose without any fructose efflux. Accordingly, since fructokinase could direct fructose flux to the pentose phosphate pathway for the supply of NADPH, fructokinase expression may be a potential strategy for enhancing amino acid production. (c) 2005 Federation of European Microbiological Societies. Published by Elsevier B.V. All rights reserved.