enzymatically by cystathionine beta-synthase and cystathionine gamma-lyase, endogenous non-enzymatic reactions, and may also be produced by the microbiome. Eventually the gas is converted to sulfite in the mitochondria by thiosulfate reductase, and the sulfite is further oxidized to thiosulfate and sulfate by sulfite oxidase. The sulfates are excreted in the urine. acts as a relaxant of smooth muscle and as a vasodilator. Though both NO and have been shown to relax blood vessels, their mechanisms of action are different: while NO activates the enzyme guanylyl cyclase, activates ATP-sensitive potassium channels in smooth muscle cells. Researchers are not clear how the vessel-relaxing responsibilities are shared between NO and . However, there exists some evidence to suggest that NO does most of the vessel-relaxing work in large vessels and is responsible for similar action in smaller blood vessels. deficiency can be detrimental to the vascular function after an acute myocardial infarction (AMI). therapy reduces myocardial injury and reperfusion complications. Due to its effects similar to NO (without its potential to form peroxides by interacting with superoxide), is now recognized as potentially protecting against cardiovascular disease. Recent findings suggest strong cellular crosstalk of NO and , demonstrating that the vasodilatatory effects of these two gases are mutually dependent. Additionally, reacts with intracellular S-nitrosothiols to form the smallest S-nitrosothiol (HSNO), and a role of in controlling the intracellular S-nitrosothiol pool has been suggested. is also active in the brain, where it increases the response of the NMDA receptor and facilitates long term potentiation, which is involved in the formation of memory. In Alzheimer's disease and Parkinson's disease the brain's concentration is severely decreased. The beneficial effects of signaling inspired pharmaceutical development initiatives. Akin to NO, presenting possible new therapy opportunities for erectile dysfunction. In 2005, it was shown that mice can be put into a state of suspended animation-like hypothermia by applying a low dosage of . Excess endogenous production of can be problematic in disorders such as trisomy 21 (Down syndrome) and type 1 diabetes. Emerging gasotransmitter candidates Many gaseous signaling molecules have been suggested to be the fourth gasotransmitter, notably methane and cyanide. External links European Network on Gasotransmitters (ENOG) References Neurotransmitters Gaseous signaling molecules