Metabolism of D-Fructose in Micro-organisms

D-Fructose transport in micro-organisms, and the rapid utilization of D-fructose by bacteria is generally assumed to require the activity of a PEP (enol pyruvate phosphate)-dependent, phosphotransferase system (PTS).169 In this system, enzyme I catalyzes the transfer of phosphate from PEP to a nitrogen atom of a histidine residue in a small, high-energy protein, HPr, according to reaction I. In a subsequent step, enzyme II, in the presence of factor III, catalyzes the transfer of 

Hanson and Anderson170 resolved the phosphorylation system of Acetobacter aerogenes into four components enzyme I, HPr, and two components required for the activity of enzyme II. The components of enzyme II are a protein of high molecular weight and a smaller, inducible protein that increases the affinity of the system for D-fructose. The D-fructose-PEP-transferase system is similar to those involved with D-fructose phosphorylation in Arthrobacter pyridinolis, and with hexose phosphorylation in Staphylococcus aureus.171 

Non-sulfur, purple, photosynthetic bacteria, Rho do spirillum rub-rum and Rhodopseudomonas spheroides172 also possess a PEP-de-pendent D-fructose phosphotransferase. Two protein fractions are required for D-fructose phosphorylation. In contrast to PEP-depend-ent, phosphotransferase systems isolated from other bacteria, the aforementioned two organisms have one active protein fraction tightly associated with the membrane fraction, while another in the crude extract is solubilized by extraction with water, and has a molecular weight of about 200,000. There is no evidence for the presence of a phosphate-carrier protein of low molecular weight like HPr.171,173 The 

Arthrobacter pyridinolis and a variety of other bacteria have a respiration-coupled, transport system (RCS) for D-fructose. 

A characteristic of the respiration-coupled, transport system is a malate-dependent uptake of D-fructose, but not of D-glucose or L- 

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