극한미생물 유래 Non-phosphorylated L-Rhamnose Pathway 연구

Abstract

L-Rhamnose (L-6-deoxy-mannose) is a deoxy sugar that is enriched in some fractions of plant and seaweed biomass, such as hemicellulose pectin, and ulvan. Currently, two major pathways for L-rhamnose degradation have been identified: phosphorylated metabolic pathway (PMP) and non-phosphorylated metabolic pathway (NMP). Many microbes including Escherichia coli convert L-rhamnose to dihydroxyacetone phosphate, which enters the glycolysis pathway, and L-lactaldehyde via PMP. Some organisms are known to metabolize L-rhamnose via NMP. Recently, we have found that Thermoplasma acidophilum (DSM1728) efficiently utilizes L-rhamnose as a carbon source and that this microorganism metabolizes L-rhamnose via the non-phosphorylated pathway. In this study, we have identified and characterized a gene cluster encoding the three metabolic enzymes, L-rhamnose dehydrogenase (TA0747P), L-rhamnonate dehydratase (TA0752), and L-KDR aldolase (TA0745), by which L-rhamnose is converted into pyruvate and L-lactaldehyde. This is the first report on the identification of the genes involved in the non-phosphorylated metabolism of L-rhamnose in Archaea.