Glycerol Kinase, the Pacemaker for the Dissimilation of Glycerol in Escherichia coli

Abstract

The activity of glycerol kinase is rate-limiting in the metabolism of glycerol by cells of Escherichia coli. A mutant strain producing a glycerol kinase resistant to inhibition by fructose-I , 6-diphosphate grows faster than its wild-type parent on glycerol as the sole source of carbon and energy. The amount of intracellular fructose-1 ,6-diphosphate was determined for wild-type cells growing exponentially on glycerol. The water content of such cells was also determined, allowing calculation of the intracellular concentration of fructose-1 ,6-diphosphate. This value, 1.7 mm, is adequate to exert substantial inhibition on the wild-type glycerol kinase. The desensitization of glycerol kinase to feedback inhibition also enhances the power of glycerol to exert catabolite repression, both on the enzymes of the glycerol system itself and on those of the lactose system. However, desensitization of glycerol kinase alone does not eliminate the phenomenon of diauxic growth in a glucose-glycerol medium. Biphasic growth in such a medium is abolished if the altered enzyme is produced constitutively. The constitutive production of the mutant kinase at high levels, however, renders the cells vulnerable to glycerol. Thus, when the cells have been grown on a carbon source with a low power for catabolite repression, e.g., succinate, sudden exposure to glycerol leads to overconsumption of the nutrient and cell death.for sensitivity of the enzyme to FDP at pH 7.5 (29). Protein was determined by the biuret reagent (8).Specific activities are expressed as micromoles of substrate converted per minute per milligram of protein at 25 C.Determination of intracellular FDP levels. Cells of strain 7 were grown in 35 ml of glycerol mineral me-753 on August 5, 2020 by guest

Thioredoxin 2 fromEscherichia coliis not involvedin vivoin the recycling process of methionine sulfoxide reductase activities

“…We found an intracellular water content of 1.5 ml per g dry weight for the LCB303 strain which is in good agreement with data from Epstein and Schultz [22], and slightly lower than that reported by Zwaig et al [23]. We further found (1) that 25% of the dry weight of the cells is cytoplasmic proteins; and (2) a water content of 6 ll mg À1 of cytoplasmic protein.…”

Catabolite repression by glucose 6‐phosphate, gluconate and lactose in Escherichia coli

“…Average values of at least three independent experiments were calculated. The following conversion factors were used to calculate the intracellular cAMP concentrations: an OD 600 of 1 corresponds to 350 g ml ¹1 dry weight, and 1 mg of dry weight corresponds to an internal volume of 2.48 l (Winkler and Wilson, 1966;Zwaig et al, 1970). For determination of the extracellular cAMP concentration, the culture was centrifuged for 2 min and the supernatant was analysed as obtained, after two-to fivefold dilution in 50 mM potassium phosphate buffer.…”

Lethal catabolism of glycerol by Bacillus amyloliquefaciens

“…Strains which are constitutive for the catabolism of glycerol (glpR-), lack feedback control of glycerol kinase by FDP (glpK i) and grown in catabolite derepressing conditions will have high levels of the faulty kinase and are rapidly killed by exposure to glycerol [10][11][12][13]. Flooding of the dihydroxyacetone phosphate pool seems to be a prerequisite for killing these cells, since a similar mutant but defective for glycerol-3-phosphate dehydrogenation is merely growth-inhibited [13]. Cells committing this lethal catabolism of glycerol excrete methylglyoxal, a bactericidal substance derived from the DHAP.…”