CO binding studies of nitric oxide synthase: effects of the substrate, inhibitors and tetrahydrobiopterin

FEBS Letters

Daff, Simon¹  Nomura, Susumu¹  Sagami, Ikuko¹  Sato, Hideaki¹  Ito, Osamu¹  Shimizu, Toru¹ 

[1] Institute for Chemical Reaction Science, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan

关键词: Carbon monoxide;    Nitric oxide synthase;    Hemoprotein;    Dissociation constant;    Rate constant;    Flash photolysis;    NOS;    nitric oxide synthase;    nNOS;    neuronal NOS;    P450;    cytochrome P450;    H4B;    (6R)-5;    6;    7;    8-tetrahydro-l-biopterin;    CaM;    calmodulin;    K d;    dissociation constant;    k on;    recombination rate constant;    EDTA;    ethylenediaminetetraacetic acid;    DTT;    dithiothreitol;    NMMA;    N G-monomethyl-l-arginine;    NAME;    N G-nitro-l-arginine methyl ester;    NIL;    N 6-(1-iminoethyl)-l-lysine;    TC;    l-thiocitrulline;    DIC;    diphenyleneiodinium chloride;    NI;    7-nitro-1H-indazole;   

DOI  :  10.1016/S0014-5793(98)00699-1

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

The dissociation constant (K _d) for CO from neuronal nitric oxide synthase heme in the absence of the substrate and cofactor was less than 10⁻³ μM. In the presence of l-Arg, it dramatically increased up to 1 μM. In the presence of inhibitors such as N ^G-nitro-l-arginine methyl ester and 7-nitroindazole (NI), the K _d value further increased up to more than 100 μM. Addition of the cofactor, 5,6,7,8-tetrahydrobiopterin (H₄B), increased the K _d value by 10-fold in the presence of l-Arg, whereas it decreased the value to less than one 250th in the presence of NI. Addition of H₄B increased the recombination rate constant (k _on) for CO by more than two-fold in the presence of l-Arg or N ⁶-(1-iminoethyl)-l-lysine, whereas it decreased the k _on value by three-fold in the presence of l-thiocitrulline. Thus, the binding fashion of some of inhibitors, such as NI, may be different from that of l-Arg with respect to the H₄B effect.

【 授权许可】

Unknown