20 Jul 2012

Dioxygen Activation in Non-heme Iron Enzymes

Five Slides About

Submitted by Gerard Rowe, University of South Carolina Aiken

This lecture provides a short introduction to the other half of biological iron chemistry:  enzymes that do not contain a porphyrin group that ligates the iron atom.  There are several important applications for non-heme iron in cells, both mammalian and bacterial.  Oxygen activating non-heme iron enzymes fall into a few basic categories and includes mononuclear iron monooxygenases and dioxygenases, and binuclear iron monooxygenases. The requirements to activate and utilize dioxygen will be given.  Examples of each type of enzyme, along with interesting catalytic intermediates implicated in their mechanisms, and the general catalytic cycles will be given.

Learning Goals: 
  • The student will be able to identify the basic roles of non-heme iron in biology.
  • The student will develop an understanding of the utility of building an enzyme with non-heme iron instead of heme iron in oxygen activation chemistry.
  • The student will be able to demonstrate the need for external reducing equivalents in dioxygen activation.
  • An advanced student will be able to apply this knowledge to choose the most appropriate enzyme type for a given chemical reaction.
Implementation Notes: 

This 5 slides would fit well after heme iron enzymes have been introduced.  To make the best use of the slides, students should be familiar with the iron-oxo motif in bioinorganic chemistry and what its reactivity is.  

An interesting discussion to have with your class would be to come up with some ideas as to why nature would choose to utilize non-heme iron over heme iron for use in oxidases.  Generally, heme iron enzymes are capable of oxidizing any C-H bond (with the possible exception of methane), so issue really becomes one of nature trying to avoid "bringing a gun to a knife fight" in terms of substrate oxidation.

Time Required: 
20-30 minutes
Evaluation Methods: 

My students always get an exam question based on a metalloenzyme that was not covered in class, but follows one of the reactivity patterns described in either the non-heme or heme lecture.  

Evaluation Results: 

In the past, my students have not done well on these questions, so I believe I need to spend more time explicitly talking about the reactivity motifs than the specifics of the enzymes themselves.  I hope these slides will help me towards that goal.

Creative Commons License: 
Creative Commons Licence


These slides are great!  I can use them both for my research students and in teaching.  Thanks.

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