Prenylcysteine oxidase that cleaves the thioether bond of prenyl-L-cysteines, such as farnesylcysteine and geranylgeranylcysteine (PubMed:9287348). Only active against free prenylcysteines and not prenylcysteine residues within prenylated proteins or peptides (PubMed:9287348). Involved in the final step in the degradation of prenylated proteins, by degrading prenylcysteines after the protein has been degraded (PubMed:9287348). an S-prenyl-L-cysteine + H2O + O2 = a prenal + H2O2 + L-cysteine H2O + O2 + S-(2E,6E)-farnesyl-L-cysteine = (2E,6E)-farnesal + H2O2 + L-cysteine [(2E,6E,10E)-geranylgeranyl]-L-cysteine + H2O + O2 = (2E,6E,10E)-geranylgeranial + H2O2 + L-cysteine Belongs to the prenylcysteine oxidase family.