Members of the heme enzyme family are uniquely diverse in structure particularly with respect to the ligand proximal to the heme, but can share similar functionality. For example, heme enzymes that have proximal histidine (e.g. hemoglobin, myoglobin, neuroglobin) and cysteine (e.g. Cyt P450s) can generate nitric oxide (NO) via nitrite reduction, and are perceived as nitrite reductases (NiRs). Here, we report the spectroscopic and electrochemical properties of human serum albumin (HSA) reconstituted with heme <i>b</i> (referred to as HSA-heme) in the presence of nitrite under oxygen-limiting conditions. HSA-heme contains a pentacoordinated heme complex via Tyr161, and reduces nitrite to nitritc oxide (NO) as supported by spectral analysis and fluorimetric assays involving the N-nitrosation of 2,3-diaminonaphthalene. Cyclic and square wave voltammetry also support this catalytic reaction, particularly when compared against electrochemical results from the more well-studied myoglobin system. Results from this work provide a better understanding on the effect of the tyrosine ligand on nitrite to NO catalysis, and will be compared against heme enzyme systems that have proximal histidine and cysteine.

Spectroscopic and electrocatalytic reduction studies of nitrite to NO by human serum albumin-heme

254th National Meeting (2017)

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