1991 Fiscal Year Final Research Report Summary
Action Mechanism of Suicide Inhibitors of Ascorbate Peroxidase
| Project/Area Number |
02556012
|
|---|
| Research Category |
Grant-in-Aid for Developmental Scientific Research (B)
|
| Allocation Type | Single-year Grants |
|---|
| Research Field |
応用生物化学・栄養化学
|
|---|
| Research Institution | Kyoto University |
|---|
Principal Investigator |
ASADA Kozi Kyoto Univ. Res. Inst. Food Sci. Professor, 食糧科学研究所, 教授 (50027182)
|
|---|
| Co-Investigator(Kenkyū-buntansha) |
ENDO Tsuyoshi Kyoto Univ. Res. Inst. Food Sci. Instr., 食糧科学研究所, 助手 (90201962)
|
|---|
| Project Period (FY) |
1990 – 1991
|
| Keywords | Ascorbate Peroxidase / Chloroplast / Monodehydroascorbate / Active Oxygen |
|---|
| Research Abstract |
1. Using different characteristics as to inhibitors and substrates, simple methods for separate assays of the two types of peroxidases, and of chloroplast and cytosol isizymes of ascorbate peroxidases (APX) were developed.
2. The hydrogen peroxide-dependent oxidation of APX from tea leaves was inhibited by thiols, such as dithiothreitol, glutathione, mercaptoethanol and cysteine. These thiols themselves did not inactivate the enzyme. However, they inactivated the enzyme when hydrogen peroxide was produced by the metal-catalyzed oxidation of thiols or when exogenous hydrogen peroxide was added. Thiols were oxidized by APX and hydrogen peroxide to thiol radicals. Inactivation of APX by thiols and hydrogen peroxide is caused by the interaction of the enzyme with the thiyl radicals produced at its reaction center.
3. The thloroplast isozyme of APX from tea leaves was digested with lysyl endopeptidase, and the amino acid sequences of the peptide fragments were determined. The sequence of the peptides from APX exhibit a higher degree of homology to the sequences of cytochrome c peroxidase than to those of guaiaeol peroxidases from plants.
4. A thylakoid-bound form of APX was found from spinach leaves. The activity of the bound form and that in siroma was 1 : 1. The thylakoid enzyme was predominantly localized in the stroma thylakoids, and solubilized only by detergents. Enzymatic properties of the thylakoid-bound APX were very similar to those of the stromal APX.
|
