Effects of carotenoids from Deinococcus radiodurans on protein oxidation

Aims: To evaluate the antioxidant effect of carotenoids from Deinococcus radiodurans on protein. Methods and Results: Deinococcus radiodurans strain R1 (ATCC 13939) and its mutant strain R1 Delta crtB were used for this study. The total carotenoids (R1ex) from D. radiodurans were obtained by extraction with acetone/methanol (7 : 2, by vol), and their antioxidant activity was measured using the DPPH center dot (2,2-diphenyl-1-picrylhydrazyl) system. The protein oxidation level, in vitro and in the cell, was measured using the DNPH (2,4-dinitrophenyl hydrazine) method. The carotenoid extract R1ex scavenged 40 center dot 2% DPPH center dot radicals compared to beta-carotene (31 center dot 7%) at a concentration of 0 center dot 5 mg ml-1. The intracellular level of protein oxidation in mutant R1 Delta crtB, which does not contain carotenoid, was 0 center dot 0212 mmol mg-1 protein which is significantly greater than that in the wild type (0 center dot 0169 mmol mg-1 protein) following the treatment with H2O2. The purified major carotenoid product (deinoxanthin) from the wild type showed a greater inhibition of oxidative damage in bovine serum albumin than lycopene or lutein. Conclusions: Carotenoids prevent protein oxidation and contribute to the resistance to cell damage in D. radiodurans. Significance and Impact of the Study: Our results provide the evidence that carotenoids can protect proteins in D. radiodurans against oxidative stress.