Near ultraviolet light inactivation of dihydroxyacid dehydratase in Escherichia coli.
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/m2/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.
John M. Dalton Research Center, University of Missouri-Columbia 65211.
E
E
Smyk-Randall
O R
OR
Brown
A
A
Wilke
A
A
Eisenstark
D H
DH
Flint
D002374:Catalase / Q000378:metabolism; D004926:Escherichia coli / Q000201:enzymology* / Q000378:metabolism / Q000528:radiation effects; D005609:Free Radicals / Q000378:metabolism; D006836:Hydro-Lyases / Q000037:antagonists & inhibitors* / Q000528:radiation effects*; D006861:Hydrogen Peroxide / Q000378:metabolism; D010084:Oxidation-Reduction; D013482:Superoxide Dismutase / Q000378:metabolism; D013481:Superoxides / Q000378:metabolism; D014466:Ultraviolet Rays
D005609:Free Radicals; D013481:Superoxides; D006861:Hydrogen Peroxide; D002374:Catalase; D013482:Superoxide Dismutase; D006836:Hydro-Lyases; C020052:dihydroxyacid dehydratase