ENZYMATIC ACTIVITY AND PARTIAL PURIFICATION OF SOLANAPYRONE SYNTHASE : FIRST ENZYME CATALYZING DIELS-ALDER REACTION

Abstract In cell-free extracts of Alternaria solani , an enzymatic activity converting prosolanapyrone II to solanapyrones A and D via oxidation and subsequent Diels–Alder reaction has been found. Chromatography with DEAE–Sepharose provided two active fractions, pools 1 and 2. The former fraction converted prosolanapyrone II to solanapyrones A and D in a ratio of 2.2:1 with optical purities of 99% and 45% ee, respectively. The latter fraction did so in a ratio of 7.6:1 with 99% and nearly 0% ee, respectively. The enzyme partially purified from pool 2 native molecular weight of 40–62 kD and a pl of 4.25. The high reactivity of prosolanapyrone III in aqueous solution and the chromatographic behavior of the enzyme in pool 2 suggest that a single enzyme catalyzes both the oxidation and Diels–Alder reaction.