Inhibition of Soluble Guanylate Cyclase by ODQ

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• 作者：Yunde Zhao ; Philip E. Brandish ; Marilena DiValentin ; Johannes P. M. Schelvis ; Gerald T. Babcock ; and Michael A. Marletta
• 刊名：Biochemistry
• 出版年：2000
• 出版时间：September 5, 2000
• 年：2000
• 卷：39
• 期：35
• 页码：10848 - 10854
• 全文大小：78K
• 年卷期：v.39,no.35(September 5, 2000)
• ISSN：1520-4995

文摘

The heme in soluble guanylate cyclases (sGC) as isolated is ferrous, high-spin, and 5-coordinate.[1H-[1,2,4]oxadiazolo-[4,3-a]quinoxalin-1-one] (ODQ) has been used extensively as a specific inhibitorfor sGC and as a diagnostic tool for identifying a role for sGC in signal transduction events. Addition ofODQ to ferrous sGC leads to a Soret shift from 431 to 392 nm and a decrease in nitric oxide (NO)-stimulated sGC activity. This Soret shift is consistent with oxidation of the ferrous heme to ferric heme.The results reported here further define the molecular mechanism of inhibition of sGC by ODQ. Additionof ODQ to the isolated sGC heme domain [es/gifchars/beta2.gif" BORDER=0 ALIGN="middle">1(1-385)] gave the same spectral changes as when sGC wastreated with ODQ. EPR and resonance Raman spectroscopy was used to show that the heme in ODQ-treated es/gifchars/beta2.gif" BORDER=0 ALIGN="middle">1(1-385) is indeed ferric. Inhibition of the NO-stimulated sGC activity by ODQ is due to oxidationof the sGC heme and not to perturbation of the catalytic site, since the ODQ-treated sGC has the samebasal activity as untreated sGC (68 ± 12 nmol min^-1 mg^-1). In addition, ODQ-oxidized sGC can bere-reduced by dithionite, and this re-reduced sGC has identical NO-stimulated activity as the originalferrous sGC. Oxidation of the sGC heme by ODQ is fast with a second-order rate constant of 8.5 × 10³M^-1 s^-1. ODQ can also oxidize hemoglobin, indicating that the reaction is not specific for the heme insGC versus that in other hemoproteins.