The present invention relates to processes for the production of mistletoe lectin polypeptides in homologous and heterologous host systems and mistletoe lectin peptides. Further, nucleic acid molecules are provided, which encode these mistletoe lectin polypeptides, and also pharmaceutical compositions comprising mistletoe lectin nucleic acids. The present invention also relates to isolated mistletoe lectin polypeptides and pharmaceutical compositions comprising said polypeptides.