Modulation of enzyme activities of a lead-adapted strain of Rhizopus arrhizus during bioaccumulation of lead.

Activity of some enzymes of a Pb-adapted strain of Rhizopus arrhizus augmented significantly during bioaccumulation of Pb from a chemically defined medium. The mycelium of a Pb-adapted strain exposed to 1 microg/mL Pb in a defined medium for 10 d at 28 +/- 2 degrees C exhibited, relative to a wild-type strain, increased activities of antioxidant enzymes, i.e. SOD, CAT and GPX and of enzymes like AP and PPO involved in defense against pathogens. Another response is a significant increase in the cellular thiol content after 4 d. The responses to Pb exposure thus include an increase in the antioxidant and anti-pathogen defense, and an increased metal-chelating ability.