A 42 kDa anionic peroxidase (EC 184.108.40.206) having a pl of 3.6 was purified from suspension cultures of cells of sycamore maple (Acer pseudoplatanus L.) grown in the dark by a combination of lectin-affinity, anion-exchange and gel permeation chromatography. The enzyme had an amino acid composition similar to that found for other anionic plant peroxidases, but the protein was blocked to amino-terminal protein sequencing. Commercially available antibodies against horseradish peroxidase were shown to cross-react with the sycamore maple enzyme on immunoblots. The purified peroxidase displayed differences in its affinity for each of the three monolignols, and these differences were compared to those found for a commercial preparation of horseradish peroxidase, as well as a laccase (p-diphenol:O2 oxidoreductase: EC 220.127.116.11) purified from sycamore maple cell suspension cultures. These results are discussed with respect to the role played by peroxidases in lignin deposition and host-pathogen response.