Cytochrome P450 monooxygenases in crustaceans

Area of Science:

• Biochemistry
• Environmental Toxicology
• Marine Biology

Background:

• The hepatopancreas is a key organ for xenobiotic metabolism in crustaceans, primarily utilizing cytochrome P450 enzymes.
• Inhibitors in hepatopancreas microsomes and cytosol have hindered in vitro studies of crustacean monooxygenase activity.
• Low NADPH cytochrome c reductase activity is common in crustacean hepatopancreas microsomes, complicating enzyme studies.

Purpose of the Study:

• To investigate the presence, purification, and characterization of cytochrome P450 enzymes in crustacean hepatopancreas.
• To determine the substrate specificity of purified crustacean cytochrome P450 enzymes.
• To explore the potential for inducing cytochrome P450 activity in crustaceans.

Main Methods:

• Chromatographic separation of cytochrome P450 from crab and spiny lobster hepatopancreas microsomes using DEAE-cellulose.
• Purification of a specific cytochrome P450 form from spiny lobster hepatopancreas.
• Reconstitution assays to assess the enzymatic activity of purified cytochrome P450 with various substrates.

Main Results:

• Cytochrome P450 enzymes were successfully resolved and purified from crustacean hepatopancreas.
• Purified spiny lobster cytochrome P450 efficiently metabolized vertebrate sex steroids (progesterone, testosterone) and xenobiotics like benzphetamine and aminopyrine.
• Ecdysone, the crustacean molting hormone, was not a substrate for the purified enzyme.
• N-demethylation of benzphetamine and aminopyrine showed the highest activities.

Conclusions:

• Crustacean hepatopancreas cytochrome P450 enzymes exhibit distinct substrate specificities, differing from the crustacean molting hormone.
• These enzymes are capable of metabolizing a range of xenobiotic compounds, indicating their role in detoxification.
• The induction of cytochrome P450 in crustaceans by common vertebrate inducers appears limited and less sensitive compared to fish.