Citrulline, nitric oxide synthesis from

Recent investigations have shed light on peculiarities of the NOS action mechanism the role of the H4B cofactor and CaM, and cooperativity in kinetic and thermodynamic properties of different components of the nitric oxide synthesis system. Stop flow experiments with eNOS (Abu-Soud et al., 2000) showed that calmodulin binding caused an increase in NADH-dependent flavin reduction from 0.13 to 86 s 1 at 10 °C. Under such conditions, in the presence of Arg, heme is reduced very slowly (0.005 s 1). Heme complex formation requires a relatively high concentration ofNO (>50 nM) and inhibits the entire process NADH oxidation and citrulline synthesis decreases 3-fold and Km increases 3-fold. NOS reactions were monitored at subzero temperatures in the presence of 50% ethylene glycol as an anti-freeze solvent (Bee et al., 1998). 

For descriptive information on the principles of the phosphor imaging process, see Klein and Clark (1993) and Clark and Klein (1996) and literature available from the companies named above. An example of a commercial instrument is shown in Figure 13.5. The method was applied to studies of drug metabolism (Nagatsuka et al., 1993 Ueda et al., 1993), iodothyronine deiodinase activity (Koopdonk-Kool et al., 1993), and citrulline synthesis by nitric oxide synthase activity (Vyas et al., 1996). The synthesis of cholesterol in rat liver was studied using a combination of bioimaging and liquid scintillation counting (Okuyama et al., 1995). 

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