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.
Smyk-Randall
E
E
John M. Dalton Research Center, University of Missouri-Columbia 65211.
Brown
O R
OR
Wilke
A
A
Eisenstark
A
A
Flint
D H
DH
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