SUMMARY: D-Glucoside 3-dehydrogenase specific acivity in was maximal towards the end of the exponential growth phase of batch cultures; over 90 % of the activity disappeared within the next 15 h. Manganese ions, although essential for growth of the organism, strongly repressed D-glucoside 3-dehydrogenase synthesis in sucrose medium but had little effect when the carbon source was methyl α-D-glucoside. D-Glucoside 3-dehydrogenase activity increased linearly with increasing specific growth rate in chemostat cultures limited by carbon, nitrogen, phosphate or manganese when methyl α-D-glucoside was the carbon source. High enzyme activity was found with sucrose as carbon source only when the growth medium was manganese-limited.

D-Glucoside 3-dehydrogenase activity disappeared from incubated in carbon- and nitrogen-free medium or in nitrogen-free medium containing succinate, but on continued incubation the activity returned and was then stable. The recovery of activity could be prevented by chloramphenicol or erythromycin. Bacteria containing the recovered dehydrogenase activity could not convert sucrose to 3-ketosucrose when oxygen acted as the terminal electron acceptor, but produced 3-ketosucrose at the normal rate in the presence of ferricyanide.

D-Glucoside 3-dehydrogenase activity disappeared irreversibly from bacteria incubated in nitrogen-free medium containing sucrose. Loss of activity followed first order kinetics in bacteria taken from nitrogen-, phosphate- or manganese-limited chemostat steady states; an accelerating rate of decay occurred in cells grown under carbon-limitation. 8-Hydroxyquinoline, chloramphenicol, erythromycin, 2,4-dinitrophenol and manganese ions could reduce the rate of decay.


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