Mechanistic Insights into the Activation of Soluble Guanylate Cyclase by Carbon Monoxide: A Multistep Mechanism Proposed for the BAY 41-2272 Induced Formation of 5-Coordinate CO–Heme

Abstract

Soluble guanylate cyclase (sGC) is a heme-containing enzyme that catalyzes cGMP production upon sensing NO. While the CO adduct, sGC-CO, is much less active, the allosteric regulator BAY 41-2272 stimulates the cGMP productivity to the same extent as that of sGC-NO. The stimulatory effect has been thought to be likely associated with Fe-His bond cleavage leading to 5-coordinate CO-heme, but the detailed mechanism remains unresolved. In this study, we examined the mechanism under the condition including BAY 41-2272, 2'-deoxy-3'-GMP and foscarnet. The addition of these effectors caused the original 6-coordinate CO-heme to convert to an end product that was an equimolar mixture of a 5- and a new 6-coordinate CO-heme, as assessed by IR spectral measurements. The two types of CO-hemes in the end product were further confirmed by CO dissociation kinetics. Stopped-flow measurements under the condition indicated that the ferrous sGC bound CO as two reversible steps, where the primary step was assigned to the full conversion of the ferrous enzyme to the 6-coordinate CO-heme, and subsequently followed by the slower second step leading a partial conversion of the 6-coordinate CO-heme to the 5-coordinate CO-heme. The observed rates for both steps linearly depended on CO concentrations. The unexpected CO dependence of the rates in the second step supports a multistep mechanism, in which the 5-coordinate CO-heme is led by CO release from a putative bis-carbonyl intermediate that is likely provided by the binding of a second CO to the 6-coordinate CO-heme. This mechanism provides a new aspect on the activation of sGC by CO.

Amelioration of Murine Macrophage Activation Syndrome by Monomethyl Fumarate in Both a Heme Oxygenase 1–Dependent and Heme Oxygenase 1–Independent Manner

“…Like nitric oxide, CO is known to bind the gaseous receptor soluble guanylyl cyclase (sGC), which converts GTP to cGMP (35,36). This biochemical step is involved in increased protein phosphorylation by the activation of protein kinases (MAP kinases) and has been studied for its antithrombotic effects, among others (37,38).…”

Role of Carbon Monoxide in Host–Gut Microbiome Communication

“…While NO and H 2 S can exert their effects through varied ways including scavenging ROS, metalloprotein binding, post-translational modification such as nitration, S-nitrosation, and S-sulfhydration/persulfidation among many others, CO’s molecular target scope is much more specific mostly only involving transition metals with specific redox states . As a signaling molecule, CO can activate or inhibit molecular targets by binding to ferrous heme within hemoproteins including soluble guanylate cyclase (sGC), cystathionine-beta synthase (CBS), , many cytochromes including cytochrome c oxidase (COX), − neuronal PAS domain protein 2 (NPAS2), and the K ATP channel as well as nonheme targets such as various metalloproteins, zinc within the catalytic center of metalloproteinases, or certain histidine residues of a calcium-dependent potassium channel. , Binding of CO to hemoproteins can be selective as exemplified by the subfamily of cytochrome P450 . Engagement of CO with these molecular targets is said to be important in several physiological processes such as the circadian rhythm, carotid body activity, and insulin secretion .…”