Degradation of cytokinins by maize cytokinin dehydrogenase is mediated by free radicals generated by enzymatic oxidation of natural benzoxazinones
Language English Country Great Britain, England Media print-electronic
Document type Journal Article, Research Support, Non-U.S. Gov't
PubMed
19912568
DOI
10.1111/j.1365-313x.2009.04071.x
PII: TPJ4071
Knihovny.cz E-resources
- MeSH
- Benzoxazines chemistry metabolism MeSH
- Biocatalysis MeSH
- Cytokinins metabolism MeSH
- Phloem enzymology MeSH
- Zea mays enzymology MeSH
- Laccase metabolism MeSH
- Molecular Structure MeSH
- Oxidation-Reduction MeSH
- Oxidoreductases metabolism MeSH
- Peroxidase metabolism MeSH
- Free Radicals metabolism MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
- Names of Substances
- Benzoxazines MeSH
- cytokinin oxidase MeSH Browser
- Cytokinins MeSH
- Laccase MeSH
- Oxidoreductases MeSH
- Peroxidase MeSH
- Free Radicals MeSH
Hydroxamic acid 2,4-dihydroxy-7-methoxy-1,4-benzoxazin-one (DIMBOA) was isolated from maize phloem sap as a compound enhancing the degradation of isopentenyl adenine by maize cytokinin dehydrogenase (CKX), after oxidative conversion by either laccase or peroxidase. Laccase and peroxidase catalyze oxidative cleavage of DIMBOA to 4-nitrosoresorcinol-1-monomethyl ether (coniferron), which serves as a weak electron acceptor of CKX. The oxidation of DIMBOA and coniferron generates transitional free radicals that are used by CKX as effective electron acceptors. The function of free radicals in the CKX-catalyzed reaction was also verified with a stable free radical of 2,2'-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid. Application of exogenous cytokinin to maize seedlings resulted in an enhanced benzoxazinoid content in maize phloem sap. The results indicate a new function for DIMBOA in the metabolism of the cytokinin group of plant hormones.
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