| Autor: |
Kerby, Nigel W., Rowell, Peter, Stewart, William D. P. |
| Zdroj: |
Archives of Microbiology; January 1986, Vol. 143 Issue: 4 p353-358, 6p |
| Abstrakt: |
The cyanobacteria Anabaena variabilis and Nostoc CAN showed a biphasic pattern of 14CH3NH3+uptake at external pH values of 7.0 and 9.0. The initial phase of uptake, which was independent of metabolism of 14CH3NH3+, was attributed to uptake via a CH3NH3+(NH4+) transport system at pH 7.0 and probably to passive diffusion of uncharged CH3NH2 and trapping by protonation at pH 9.0. The second slower phase of uptake was attributed to metabolism of CH3NH3+via glutamine synthetase to form ?-methylglutamine which accumulates. Anabaena cylindrica showed an initial rapid uptake at pH 7.0 and pH 9.0 but metabolism of 14CH3NH3+was undetectable at pH 7.0 and was barely detectable at pH 9.0. Pretreatment of A. variabilis with l-methionine-d,l-sulphoximine to inactivate glutamine synthetase, inhibited the second phase of 14CH3NH3+uptake at both pH 7.0 and pH 9.0 and the accumulation of ?-methylglutamine but had no effect on the first phase of uptake. Following transfer of A. variabilis to darkness the initial phase of 14CH3NH3+uptake at pH 7.0 and 9.0 was unaffected but the subsequent metabolism via glutamine synthetase was inhibited. |
| Databáze: |
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