A novel lyase, combining hydratase and aldolase activity, that converts citral into methylheptenone and acetaldehyde, was purified from spores of Penicillium digitatum. Remarkably, citral lyase activity was induced 118-fold by incubating nongerminating spores with the substrate, citral. This cofactor independent hydratase/aldolase, was purified and found to be a monomeric enzyme of 31 kDa. Citral lyase has a Km of 0.058 mm and a Vmax of 52.6 U?mg1. Enzyme activity was optimal at 20 °C and pH 7.6. The enzyme has a strong preference for the trans isomer of citral (geranial). Citral lyase also converts other ,-unsaturated aldehydes (farnesal, methyl-crotonaldehyde, decenal and cinnemaldehyde).