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K J Monty

Publications and source records attributed to K J Monty.

12 recordsLinked to original sources
PubMed1979

Glutamine as a feedback inhibitor of the Rhodopseudomonas sphaeroides nitrogenase system.

In whole cells of Rhodopseudomonas sphaeroides, nitrogen fixation, as measured by hydrogen production and acetylene reduction, was totally inhibited by micromolar concentrations of ammonia. This inhibition could not be duplicated by glutamate or glutamine alone. The inhibition by ammonia was abolished by methionine sulfoximine, a glutamine synthetase inhibitor. Inhibition by glutamine was complete in the presence of methionine sulfone, a preferential inhibitor of glutamate synthase, presumably by permitting a rise in the glutamine pool. The results indicated that the level of the glutamine pool controlled the activity of nitrogenase. None of these effects could be duplicated with cell-free nitrogenase, indicating there is probably a mediator which responds to the glutamine pool and inhibits nitrogenase, rather than glutamine itself being a direct inhibitor.

Ammonia↗
PubMed1976

Regulatory mutants and control of cysteine biosynthetic enzymes in Salmonella typhimurium.

The cysB region in Salmonella typhimurium regulates in a positive manner the noncontiguous structural genes for the enzymes responsible for sulfate reduction in cysteine biosynthesis. We treated three cysB mutants with chemical mutagens and selected 81 secondary mutants in which the inability to utilize sulfate was suppressed. Growth experiments on the suppressed mutants showed that the original loss of sulfate utilization had been corrected to varying degrees and that portions of the pathway had been established in abnormal relationship to one another. Sixty of the suppressed mutations were mapped via transductional analysis, and each was very closely linked to the original cysB mutation. We demonstrated that the cysB product functions in the regulation of the cysteine biosynthetic enzymes during both logarithmic growth and stationary phase. Mutation can alter the regulatory response of one enzyme in either an upward or downward direction while the regulation of other enzymes in the pathway remains unchanged. These data are consistent with the idea of a multivalent or multisite regulator molecule.

Cell-Free System↗
PubMed1975

Cysteine biosynthesis in Salmonella typhimurium: the presence of ATP-sulfurylase and APS-kinase in various cysteine-requiring mutants.

Enzymatic tests were performed on a series of cysteine-requiring mutants for the presence of the sulfate activating enzymes. ATP-sulfurylase (sulfate adenylyltransferase EC 2.7.7.4) and APS-kinase (adenylylsulfate kinase EC 2.7.1.25). The enzymatic products adenosine 5'-[35S]sulfatophosphate and adenosine 3'-phosphate 5'-[35S]sulfatophosphate were identified by paper electrophoresis and measured quantitatively without elution from the paper. Cys mutants mapping in cistrons, A, H, I, J, G, and Ea contain both enzymes. Mutation in the D cistron leads to the loss of ATP-sulfurylase. Mutants mapping in the C cistron lack APS-kinase. Ba, Bb, and Bc mutants lack both enzymes. The control of the synthesis of these enzymes by cysteine was examined. Both enzymes are missing when cells are grown on cysteine.

Adenosine Triphosphate↗