| Abstract: | Previous studies showed that Arthrobacter pyridinolis can transport and utilize d-glucose only after prior growth on certain Krebs cycle intermediates. In contrast, we found that d-fructose was taken up and metabolized by A. pyridinolis without special prior conditions of growth. d-Fructose was first converted to d-fructose-1-phosphate by a phosphoenolpyruvate (PEP):D-fructose phosphotransferase. This activity required both supernatant and pellet fractions from d-fructose-grown cells centrifuged at 150,000 x g. The d-fructose-1-phosphate formed was converted to d-fructose-1, 6-diphosphate. Mutants deficient in PEP:d-fructose phosphotransferase and d-fructose-1-phosphate kinase, or d-fructose-1, 6-diphosphatase (FDPase) were unable to grow on d-fructose but retained the normal ability to use d-glucose. Mutants forming reduced amounts of FDPase were completely unable to grow on d-fructose but were still capable of limited growth on Krebs cycle intermediates. A requirement for higher levels of FDPase for growth on d-fructose than for growth on Krebs cycle intermediates was also indicated by the higher specific activities of FDPase in d-fructose-grown cells than in cells grown on l-malate or amino acids. |
