Conversion of 1′-deoxy-2H-ABA to2H-ABA in cell-free extracts fromCercospora rosicola

Autor: Laila F. Al-Nimri, Ronald C. Coolbaugh
Rok vydání: 1991
Předmět:
Zdroj: Journal of Plant Growth Regulation. 10:63-66
ISSN: 1435-8107
0721-7595
DOI: 10.1007/bf02279313
Popis: Abscisic acid (ABA) biosynthesis in the fungusCercospora rosicola has been studied previously by feeding potential intermediates to growing cultures and examining the products. The present work describes the isolation and partial characterization of an enzyme system which catalyzes the last step in this pathway, the conversion of 1′-deoxy-2H-ABA to2H-ABA. Enzyme extracts were prepared from cold-pressed mycelia of actively growingC. rosicola in tricine buffer containing sucrose and β-mercaptoethanol. Low-speed supernatants and resuspended microsomal preparations were active in converting 1′-deoxy-2H-ABA to2H-ABA. Optimum conditions for the reactions were established at 10 μM substrate, 300 μl enzyme extract in a total volume of 1 ml. Reaction products were chromatographed by reverse-phase high-performance liquid chromatography (HPLC). The presumptive ABA fractions were collected and the2H-ABA was measured by combined gas chromatography-mass spectrometry (GC-MS) with an2H-ABA standard. Most of the enzyme activity was found in the microsomal fraction. Typical reaction rates were on the order of 1.5 pmol2H-ABA formed/min/mg protein. The reaction required NADPH and was enhanced by FAD. Triarimol, a substituted pyrimidine, which inhibits ABA synthesis inC. rosicola, had no effect on the conversion of 1′-deoxy-2H-ABA to2H-ABA.
Databáze: OpenAIRE
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