Abstract
Induced formation of tryptophanase in Escherichia coli B/r is temporarily inhibited by near-ultraviolet (UV) irradiation. The inhibition is greater when irradiation is at 5 C than when at room temperature. Hence, the inhibition is the result of a photochemical, rather than photoenzymatic, alteration of some cellular component. The action spectrum has a peak in the region of 334 nm and is similar to that for growth delay. However, inhibition of tryptophanase formation is more sensitive to near-UV irradiation than are growth, respiration, and the induced formation of β-galactosidase. Thus, for tryptophanase the lack of formation cannot be due to general inhibition of metabolism. Pyridoxal phosphate absorbs in the near-UV region of the spectrum and is a cofactor for tryptophanase, but this enzyme in induced cells is not inactivated by near UV-radiations. An experiment in which toluene-treated suspensions from irradiated and unirradiated cells were mixed showed that irradiation does not cause the formation of an inhibitor of tryptophanase activity. The possibility remains that the absorption of radiant energy by pyridoxal phosphate interferes with the synthesis of tryptophanase.
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Selected References
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- JAGGER J. A small and inexpensive ultraviolet dose-rate meter useful in biological experiements. Radiat Res. 1961 Apr;14:394–403. [PubMed] [Google Scholar]
- JAGGER J., LATARJET R. Spectres d'action de la photo-restauration chez E. coli B/r. Ann Inst Pasteur (Paris) 1956 Dec;91(6):858–873. [PubMed] [Google Scholar]
- KASHKET E. R., BRODIE A. F. Effects of near-ultraviolet irradiation on growth and oxidative metabolism of bacteria. J Bacteriol. 1962 May;83:1094–1100. doi: 10.1128/jb.83.5.1094-1100.1962. [DOI] [PMC free article] [PubMed] [Google Scholar]
- MOROWITZ H. J. Absorption effects in volume irradiation of microorganisms. Science. 1950 Mar 3;111(2879):229–229. doi: 10.1126/science.111.2879.229-a. [DOI] [PubMed] [Google Scholar]
- Morino Y., Snell E. E. The relation of spectral changes and tritium exchange reactions to the mechanism of tryptophanase-catalyzed reactions. J Biol Chem. 1967 Jun 25;242(12):2800–2809. [PubMed] [Google Scholar]
- PARDEE A. B., PRESTIDGE L. S. INACTIVATION OF BETA-GALACTOSIDASE INDUCTION BY ULTRAVIOLET LIGHT. Biochim Biophys Acta. 1963 Dec 20;76:614–621. [PubMed] [Google Scholar]
- PARDEE A. B., PRESTIDGE L. S. The initial kinetics of enzyme induction. Biochim Biophys Acta. 1961 Apr 29;49:77–88. doi: 10.1016/0006-3002(61)90871-x. [DOI] [PubMed] [Google Scholar]