Gene/Protein
Disease
Symptom
Drug
Enzyme
Compound
Pivot Concepts:
Gene/Protein
Disease
Symptom
Drug
Enzyme
Compound
Target Concepts:
Gene/Protein
Disease
Symptom
Drug
Enzyme
Compound
Query: EC:1.10.3.3 (
ascorbate oxidase
)
778
document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)
Glutathione dehydrogenase (EC 1.8.5.1) was partially purified from pea shoots. The pH optimum was 7.6. The K(m) values for GSH and dehydroascorbate were 4.4 and 0.44 millimolar, respectively. The enzyme was inhibited by iodoacetate and CuSO(4) but not significantly by ZnCl(2) or
NaN
(3). Part of the total enzyme activity was associated with isolated chloroplasts.Illuminated ruptured chloroplasts, in the presence of 50 micromolar NADP(H) and substrate concentrations of GSH or GSSG, catalyzed (dehydroascorbate plus glutathione)-dependent O(2) evolution with the concomitant reduction of dehydroascorbate to ascorbate. Oxidation of ascorbate by
ascorbate oxidase
activity associated with the chloroplasts was relatively insignificant. ZnCl(2) inhibited (dehydroascorbate plus glutathione)-dependent O(2) evolution but not ascorbate formation. The reaction was attributed to light-dependent reduction of GSSG (involving glutathione reductase) coupled to the reduction of dehydroascorbate (involving glutathione dehydrogenase). Light-dependent reduction of GSSG appears to be the rate-limiting step in this reaction sequence at physiological concentrations of GSH.
...
PMID:Light-dependent reduction of dehydroascorbate by ruptured pea chloroplasts. 1666 43
Low light intensity is common in northern China due to fog or haze, and causes stress for crop plants. To solve the problem of low light intensity stress on the growth and development of vegetable crops in China, new cropping strategies must be developed. We previously showed that an appropriate ratio of ammonium and nitrate (NH
4
+
:NO
3
-
) can alleviate the effect of low light stress on plants, although it is not clear what mechanism is involved in this alleviation. We propose the hypothesis that an appropriate ammonium/nitrate ratio (10:90) can induce NO synthesis to regulate the AsA-GSH cycle in mini Chinese cabbage seedlings under low light intensity. To test the hypothesis, we conducted a series of hydroponic experiments. The results indicated that, under low light intensity conditions, appropriate NH
4
+
:NO
3
-
(N, NH
4
+
:NO
3
-
= 10:90) decreased the contents of malondialdehyde (MDA), hydrogen peroxide (H
2
O
2
), and superoxide anion (O
2
-
) in leaves compared with nitrate treatment. Exogenous nitric oxide (SNP) had the same effects on MDA, H
2
O
2
, and O
2
-
. However, with the addition of a NO scavenger (hemoglobin, Hb) and NO inhibitors (N-nitro-l-arginine methyl ester, L-NAME),
NaN
3
(NR inhibitor) significantly increased the contents of MDA, H
2
O
2
, and O
2
-
. The application of N solution enhanced the AsA-GSH cycle by increasing the activities of ascorbate peroxidase (APX), glutathione reductase (GR), monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR), and
ascorbate oxidase
(
AAO
), compared with control (NH
4
+
:NO
3
-
= 0:100). Meanwhile, exogenous SNP significantly increased the above indicators. All these effects of N on AsA-GSH cycle were inhibited by the addition of Hb, L-NAME and
NaN
3
in N solution. The results also revealed that the N and SNP treatments upregulated the relative expression level of
GR, MDHAR1, APXT, DHAR2
, and
AAO
gene in mini Chinese cabbage leaves under low light stress. These results demonstrated that the appropriate NH
4
+
:NO
3
-
(10:90) induced NO synthesis which regulates the AsA-GSH cycle in mini Chinese cabbage seedlings under low light stress.
...
PMID:Nitric Oxide Is Involved in the Regulation of the Ascorbate-Glutathione Cycle Induced by the Appropriate Ammonium: Nitrate to Mitigate Low Light Stress in
Brassica pekinensis
. 3171 21
