Elucidation of Reaction Mechanisms of Biological Nitric Oxide by Vibrational Spectroscopy

从牛肺中提取了可溶性鸟苷环化酶(SGC)，研究了在GTP存在和不存在的情况下，还原的、CO结合的(CO-sGC)、非结合的(NO-sGC)、氧化的和氧化的非结合形式的共振拉曼光谱。，但在GTP存在下，NO-sGC的表观RR谱随时间和浓度的变化而变化。在没有GTP的情况下，N-O伸展(nu&lt；NO&gt；)和Fe-非伸展(nu&lt；Fe-NO&gt；)的RR谱带分别出现在1679和521 cm^&lt；-1&gt；在其存在下，可获得两种类型的RR光谱，但在酶反应耗尽所有GTP后，恢复了不含GTP的光谱。在一种类型的RR谱中，没有检测到非同位素敏感带，并且在另一种类型的RR谱中，它是一个五配位铁的高自旋型光谱。在另一种类型中，在1700和1681 cm；-1&gt；处观察到两条nu&lt；no&gt；带，它们分别表现出21和34 cm^&lt；-1&gt；无同位素频移。讨论了反应中间体产生的两种RR谱的结构含义。

Soluble guanylate cyclase (sGC) was isolated from bovine lung and its resonance Raman (RR) spectra were investigated for the reduced, CO-bound (CO-sGC), NO-bound (NO-sGC), oxidized, and oxidized NO-bound forms in the presence and absence of GTP.The RR spectra of sGC and CO-sGC,including the Fe-His stretch at 204 cm^<-1> and Fe-CO stretch at 473 cm^<-1>, were unaltered by binding of GTP,but apparent RR spectra of NO-sGC in the presence of GTP changed with time and concentrations of GTP.In the absence of GTP,the RR bands of N-O stretch (nu_<NO>) and Fe-No stretch (nu_<Fe-NO>) were observed at 1679 and 521 cm^<-1>, respectively. In its presence, two types of RR spectra were obtained, but after all GTP was exhausted by the enzymatic reaction, the spectrum for the absence of GTP was restoed. In one type of RR spectra, which appeared prior to the other, no NO-isotope sensitive band was detected and is heme spectrum was of a five-coordinate ferric high-spin type. In the other type, two nu_<NO> bands were observed at 1700 and 1681 cm^<-1>, which exhibited ^<15>NO isotopic frequency shifts of 21 and 34 cm^<-1>, respectively. Structural implications of the two types of RR spectra arizing from reaction intermediates have been discussed.