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. Author manuscript; available in PMC: 2013 May 15.
Published in final edited form as: Nitric Oxide. 2012 Mar 29;26(4):251–258. doi: 10.1016/j.niox.2012.03.005

Figure 2. Myoglobin is a normoxic NO dioxygenase and hypoxic nitrite reductase.

Figure 2

In normoxia, NOS enzymatically generates NO which is inactivated by oxygenated myoglobin, preventing respiratory inhibition (left side). As oxygen levels begin to decrease, and endogenous sources of NO are inhibited (nitric oxide synthase KM for oxygen ~10-20μM), myoglobin becomes deoxygenated (P50= 3.1 μM) and shifts to nitrite reduction to generate NO and inhibit respiration, thereby conserving existing oxygen.