Polyacrylamide gel electrophoresis was used for studying the protein and several isoenzymes of biomass in two kinds of photosynthetic bacteria (PSB) transforming mistletoe culture fluid (PSBT), pure PSB culture fluid as control. The proteinogram and the zymograms demonstrated that proteins, esterase isoenzyme (EST) and peroxidase isoenzyme (POD) of PSB in PSBT changed, i.e. the expression of some proteins, EST and POD of PSB were inhibited, while some new proteins, EST and POD of PSB in PSBT appeared. The expression of superoxide dismutase (SOD) of PSB in PSBT did not alter evidently. The results showed that PSB could be induced to generate new protiens, EST and POD by mistletoe, and which might take part in biotransformation of mistletoe. The research provided basis for studying the biotransformation mechanism of mistletoe by PSB and the further application of mistletoe to tumor therapy.