Ascorbate free radical reductase activity in vertebrate lenses of certain species.
OBJECTIVE
To clarify the function of ascorbate free radical (AFR) reductase in the antioxidation system of different vertebrate lenses.


METHODS
The soluble and insoluble fractions were prepared from bullfrog, guinea pig, rat, rabbit, swine, and bovine lenses, and membrane-bound enzymes in the insoluble fraction were extracted by 0.3% Triton X-100. Ascorbate free radical reductase and diaphorase activities in each fraction were determined.


RESULTS
Ascorbate free radical reductase activity in the lens soluble fraction was the highest in the bullfrog. That in the guinea pig and rabbit was at the next level. There was only a little activity in rat and swine lenses, and none was detected in the bovine lenses. However, a large species difference in AFR reductase activity was not observed in the 0.3% Triton X-100 extracts. Diaphorase activity was three to nine higher than AFR reductase activity in the soluble fractions of bullfrog, guinea pig, and rabbit. In the 0.3% Triton X-100 extracts of all animal species used, it was very high, 108 to 311 times the AFR reductase activity.


CONCLUSIONS
These results indicate that the lens soluble and membrane-bound AFR reductase in the different animals may be individual enzyme molecules and have different antioxidative functions. Because the lenses of bullfrog, guinea pig, and rabbit are known to contain a near-ultraviolet (UV) light-absorbing compound, reduced pyridine nucleotide, at a high concentration, the soluble AFR reductase activity is expected to be high in the vertebrate lenses with a near-UV light filter, to enhance the antiphoto-oxidation capacity of ascorbate.
Matsukura
S
S
Department of Ophthalmology, Tokai University School of Medicine, Isehara, Japan.
Bando
M
M
Obazawa
H
H
Oka
M
M
Takehana
M
M
D000818:Animals; D000975:Antioxidants / Q000378:metabolism; D002417:Cattle; D008058:Dihydrolipoamide Dehydrogenase / Q000378:metabolism; D006168:Guinea Pigs; D007908:Lens, Crystalline / Q000201:enzymology*; D009247:NADH, NADPH Oxidoreductases / Q000378:metabolism*; D011817:Rabbits; D011892:Rana catesbeiana; D051381:Rats; D017208:Rats, Wistar; D012995:Solubility; D013045:Species Specificity; D013552:Swine; D014714:Vertebrates / Q000378:metabolism*
D000975:Antioxidants; D009247:NADH, NADPH Oxidoreductases; C023927:monodehydroascorbate reductase (NADH); D008058:Dihydrolipoamide Dehydrogenase