The protein involved in the conversion of arteannuin B to artemisinin has been purified from the leaves of Artemisia annua, The pure protein found to be homogenous on Native gel electrophoresis showed two major bands of 21 and 11 kDa on 12% SDS-PAGE. Molecular weight estimation of native protein indicated an apparent molecular mass of 66,000 Daltons, This protein is able to achieve 58% conversion. It has a K-m of 0.5 mM for arteannuin B and a pH optima between 7.0-7.2. It is maximally active at 30 degreesC.