The structure of heme proteins Compounds I and II: some misconceptions

Area of Science:

• Biochemistry
• Chemical Biology
• Enzymology

Background:

• Heme proteins catalyze reactions involving heme oxidation to ferric states.
• Intermediates Compound I and Compound II are crucial in these reactions.
• Current notations for these intermediates are ambiguous and lead to misinterpretations.

Purpose of the Study:

• To promote uniform and chemically correct notations for heme protein intermediates.
• To address errors and misinterpretations arising from varied notations.
• To propose a new notation for the iron-oxygen bond in Compounds I and II.

Main Methods:

• Literature review of existing notations for heme intermediates.
• Analysis of chemical structures and reactivity of Compounds I and II.
• Proposal of a novel notation for the iron-oxygen bond.

Main Results:

• Identified significant ambiguities in current notations (e.g., FeIV=O vs. Fe+=O).
• Highlighted inaccuracies in representing the oxidation state and iron-oxygen bond.
• Questioned the charge localization on the porphyrin ring radical in some cases.

Conclusions:

• Existing notations for heme protein intermediates Compound I and Compound II are problematic.
• A standardized and chemically accurate notation system is needed.
• The proposed notation aims to enhance clarity and prevent errors in biochemical literature.