Cell-free conversion of 1'-deoxy-2H-ABA to 2H-ABA in extracts from Cercospora rosicola

The characteristics of the enzyme converting 1'-deoxy-ABA into ABA have been studied in the fungus C. rosicola. Enzyme extracts were prepared from cold-pressed mycelia of C. rosicola. The suspension was a high speed supernatant and a microsomal fraction. A cell-free system was developed to convert 1'-deoxy-2H-ABA into 2H-ABA using a reaction mixture containing 300 μl enzyme extract, 10 μm 1'-deoxy-2H-ABA. The reaction products were chromatographed by reverse phase HPLC. The presumptive ABA fractions were collected and 2H-ABA was quantified by GC-MS using a 2H-(2Z, 4E)-ABA standard curve. 1'-deoxy-2H-ABA was converted to an average of 1.47 pmole 2H-ABA/mg protein per min. Most of the enzymic activity was found in the microsomal fraction. The reaction required NADPH and was enhanced by FAD. The reaction was not inhibited by triarimol