Near ultraviolet light inactivation of dihydroxyacid dehydratase in Escherichia coli

• Published in: Free radical biology & medicine Vol. 14; no. 6; pp. 609 - 613
• Main Authors: Smyk-Randall, E., Brown, O.R., Wilke, A., Eisenstark, A., Flint, D.H.
• Format: Journal Article
• Language: English
• Published: New York, NY Elsevier Inc 01.06.1993; Elsevier Science
• Subjects: Biological and medical sciences; Catalase; Catalase - metabolism; Dihydroxyacid dehydratase; Escherichia coli - enzymology; Escherichia coli - metabolism; Escherichia coli - radiation effects; Free radicals; Free Radicals - metabolism; Fundamental and applied biological sciences. Psychology; Hydro-Lyases - antagonists & inhibitors; Hydro-Lyases - radiation effects; Hydrogen Peroxide - metabolism; Miscellaneous; Molecular biophysics; Near ultraviolet light; Oxidant stress; Oxidation-Reduction; Oxygen radicals; Radiation-biomolecule interaction; Superoxide dismutase; Superoxide Dismutase - metabolism; Superoxides - metabolism; Toxicity mechanisms; Ultraviolet Rays; Oxygen radicals; Toxicity mechanisms; Free radicals; Dihydroxyacid dehydratase; Catalase; Superoxide dismutase; Near ultraviolet light; Oxidant stress; Specific activity; Near ultraviolet radiation; Enzymatic activity; Enzyme; Escherichia coli; Bacteria; Biological effect; Enterobacteriaceae
• ISSN: 0891-5849; 1873-4596
• DOI: 10.1016/0891-5849(93)90142-H

The effects of near ultraviolet (NUV) light on a NUV chromophore-containing oxidant-sensitive enzyme, dihydroxyacid dehydratase (DHAD), were measured in seven strains of Escherichia coli. The strains differed in production of the oxidant-defense enzymes, superoxide dismutases (Fe-SOD and Mn-SOD), and catalases HPI and HPII. With the stress of aerobic growth but without NUV exposure, the strains lacking either Fe or Mn SOD or both SODs had 57%, 25%, and 12%, respectively, of the DHAD-specific activity of the parent (K12) strain. Under the same conditions, the catalase strains that were wild type, overproducing, and deficient had comparable DHAD-specific activities. When aerobic cultures were exposed for 30 min to NUV with a fluence of 216 J/m 2/s at 310–400 nm, the percentage decreases in DHAD-specific activities were similar (ranging from 75% to 89%) in strains with none, either, or both SODs missing, and in the catalase-overproducing strain. However, the decreases were only 58% and 52% in the strain with catalase missing and in its parent, respectively. The NUV-induced loss of DHAD enzyme activity was not accompanied by any detectable loss of the DHAD protein as measured by polyclonal antibody to DHAD.