L‐Rhamnose utilisation in Salmonella typhimurium

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Abstract
L-Rhamnose is degraded by strains of S. typhimurium by isomerization to L-rhamnulose, phosphorylation to L-rhamnulose-1-phosphate and cleavage to lactaldehyde and dihydroxyacetone phosphate. The enzymes involved are, respectively, rhamnose isomerase (RhaI), rhamnulokinase (RhuK) and an aldolase (Ald). Strains able to grow rapidly on L-rhamnose contained a high-affinity uptake system for 3H-L-rhamnose that was induced by L-rhamnose and repressed by D-glucose. The synthesis of RhaI and RhuK was also induced by L-rhamnose but was not repressed by D-glucose. The synthesis of Ald was constitutive. Data are presented on some strains which grow very slowly on L-rhamnose and on others which do not utilize it.