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Table 3.1: Properties of nitric oxide
Molecular weight 30.006 (1 mol= 0.030006 kg)
N...O bond distance 1.1508 angstroms
Partition coefficient approximately 20
Saturated NO solution approximately 3mM
Oxidation products Nitrite, nitrate
Dissociation t lze Hb-NO approximately 3 hours
Absolute density 101.325 kPa at 25oC
Solubility in H2O at OoC
Solubility in HzO at 2OoC
Solubility in H2O at 6OoC
7.34 ml/100m1
4.6 m/100m1
2.37 m/100m1
This table is modified from Archer S. Measurement of nitric oxide in biological models FASEB Journal.
1 993; 7(2): 349-60 (Archer 1 99s).
NO is generated by the stereospecific enzyme NOS which acts on L-arginine cleaving the
terminal guanidino nitrogen to produce NO and L-citrulline. This is accomplished via five
separate steps and requires 3 co-factors [tetrahydrobiopterin (BH4) and flavoproteins; flavin
adenosine dinucleotide (FAD), flavin mononucleotide (FMN)], and 2 co-substrates [oxygen
and nicotinamide adenosine dinucleotide phosphate (NADPH)I in the presence of calmodulin
and calcium (Kwon, Nathan et al. 1990; Stuehr, Kwon et al. 1991; Barnes and Belvisi 1993:
Knowles and Moncada 1994). L-arginine is a semi-essential non-aromatic amino acid and is
present in nuts (especially brazils and almonds), shellfish, and meat (bacon, beef and game)
(Vallance and Collier 1994). The necessary elements are demonstrated in figure 3.2.
Figure 3.2: The reaction to generate nitric oxide
t{Tglnlna-...+
l+ttrullino
The formation of No by No synthase involves the conversion of L-arginine to L-citrulline with several
co-facto.rs including the flavones and the tetrahydrobiopterin. There are a number of known
competitive
-nitrite,
inhibitors for the NO synthase enzym-es. NCj itselt can oxidiseO to nitrate or
perioxyitrite.
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