| Budget Amount *help |
¥3,300,000 (Direct Cost: ¥3,300,000)
Fiscal Year 1999: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 1998: ¥2,600,000 (Direct Cost: ¥2,600,000)
|
|---|
| Research Abstract |
Ascorbate free radical (AFR) reductase in the human lens soluble fraction is an important enzyme to maintain ascorbate in the reduced state, and also has diaphorase activity, and is separated into many isoforms in a similar manner as the heterogeneity of beta/gamma-crystallins by isoelectric focusing.
In this study, at first, it has been expected that amino acid sequences may be determined partially in single subunits of main isoforms of human lens soluble AFR reductases obtained after two-dimensional electrophoresis, and then, molecular diversity of the reductases may be elucidated from differences in primary structure among individual isoforms. However, the analysis of amino acid sequences did not succeed because of too small amounts of isolated protein. Analysis of amino acid sequences of rabbit lens soluble AFR reductases has been also tried, but the results are not obtained as yet.
In this study, whereas, AFR reductase and diaphorase activities in the soluble and insoluble fractions of different vertebrate lenses have been determined, and some interesting results have been obtained as follows. AFR reductase in the lens is divided into two types of soluble and membrane-bound enzymes, and they are supposed to be individual enzyme molecules and have different functions owing to their different activity ratios to diaphorase and so on. The soluble AFR reductase activity is high in the vertebrate (human, frog, guinea pig, rabbit) lenses with the function of near UV light filter, but the membrane-bound AFR reductase seems to play roles in reduction of oxidants and ascorbate regeneration in the neiborhood of the lens cell membrane in either species. Molecular diversity of the lens AFR reductases may be due to adaptation to reducing a wide variety of oxidants generated in photochemical reactions and near the cell membrane, but this conclusion needs further investigation.
|
