Reaction Process: BioCyc:META_PWY-5332

Hydrogen sulfide

H2S (33.9877212)

Hydrogen sulfide, also known as h2s or acide sulfhydrique, is a member of the class of compounds known as other non-metal sulfides. Other non-metal sulfides are inorganic compounds containing a sulfur atom of an oxidation state of -2, in which the heaviest atom bonded to the oxygen belongs to the class of other non-metals. Hydrogen sulfide can be found in a number of food items such as small-leaf linden, agar, devilfish, and nutmeg, which makes hydrogen sulfide a potential biomarker for the consumption of these food products. Hydrogen sulfide can be found primarily in blood and feces, as well as throughout most human tissues. Hydrogen sulfide exists in all living species, ranging from bacteria to humans. In humans, hydrogen sulfide is involved in a couple of metabolic pathways, which include cysteine metabolism and cystinosis, ocular nonnephropathic. Hydrogen sulfide is also involved in beta-mercaptolactate-cysteine disulfiduria, which is a metabolic disorder. Moreover, hydrogen sulfide is found to be associated with hydrogen sulfide poisoning. Hydrogen sulfide is a non-carcinogenic (not listed by IARC) potentially toxic compound. Hydrogen sulfide often results from the microbial breakdown of organic matter in the absence of oxygen gas, such as in swamps and sewers; this process is commonly known as anaerobic digestion. H 2S also occurs in volcanic gases, natural gas, and in some sources of well water. The human body produces small amounts of H 2S and uses it as a signaling molecule . Treatment involves immediate inhalation of amyl nitrite, injections of sodium nitrite, inhalation of pure oxygen, administration of bronchodilators to overcome eventual bronchospasm, and in some cases hyperbaric oxygen therapy (HBO). HBO therapy has anecdotal support and remains controversial (L1139) (T3DB). Hydrogen sulfide is a highly toxic and flammable gas. Because it is heavier than air it tends to accumulate at the bottom of poorly ventilated spaces. Although very pungent at first, it quickly deadens the sense of smell, so potential victims may be unaware of its presence until it is too late. H2S arises from virtually anywhere where elemental sulfur comes into contact with organic material, especially at high temperatures. Hydrogen sulfide is a covalent hydride chemically related to water (H2O) since oxygen and sulfur occur in the same periodic table group. It often results when bacteria break down organic matter in the absence of oxygen, such as in swamps, and sewers (alongside the process of anaerobic digestion). It also occurs in volcanic gases, natural gas and some well waters. It is also important to note that Hydrogen sulfide is a central participant in the sulfur cycle, the biogeochemical cycle of sulfur on Earth. As mentioned above, sulfur-reducing and sulfate-reducing bacteria derive energy from oxidizing hydrogen or organic molecules in the absence of oxygen by reducing sulfur or sulfate to hydrogen sulfide. Other bacteria liberate hydrogen sulfide from sulfur-containing amino acids. Several groups of bacteria can use hydrogen sulfide as fuel, oxidizing it to elemental sulfur or to sulfate by using oxygen or nitrate as oxidant. The purple sulfur bacteria and the green sulfur bacteria use hydrogen sulfide as electron donor in photosynthesis, thereby producing elemental sulfur. (In fact, this mode of photosynthesis is older than the mode of cyanobacteria, algae and plants which uses water as electron donor and liberates oxygen). Hydrogen sulfide can be found in Alcaligenes, Chromobacteriumn, Klebsiella, Proteus and Pseudomonas (PMID: 13061742). D018377 - Neurotransmitter Agents > D064426 - Gasotransmitters D004785 - Environmental Pollutants > D000393 - Air Pollutants

Hydrogen

H2 (2.0156492)

Hydrogen is a colorless, odorless, nonmetallic, tasteless, highly flammable diatomic gas with the molecular formula H2. With an atomic weight of 1.00794, hydrogen is the lightest element. Besides the common H1 isotope, hydrogen exists as the stable isotope Deuterium and the unstable, radioactive isotope Tritium. Hydrogen is the most abundant of the chemical elements, constituting roughly 75\\% of the universes elemental mass. Hydrogen can form compounds with most elements and is present in water and most organic compounds. It plays a particularly important role in acid-base chemistry, in which many reactions involve the exchange of protons between soluble molecules. Oxidation of hydrogen, in the sense of removing its electron, formally gives H+, containing no electrons and a nucleus which is usually composed of one proton. That is why H+ is often called a proton. This species is central to discussion of acids. Under the Bronsted-Lowry theory, acids are proton donors, while bases are proton acceptors. A bare proton H+ cannot exist in solution because of its strong tendency to attach itself to atoms or molecules with electrons. However, the term proton is used loosely to refer to positively charged or cationic hydrogen, denoted H+. H2 is a product of some types of anaerobic metabolism and is produced by several microorganisms, usually via reactions catalyzed by iron- or nickel-containing enzymes called hydrogenases. These enzymes catalyze the reversible redox reaction between H2 and its component two protons and two electrons. Creation of hydrogen gas occurs in the transfer of reducing equivalents produced during pyruvate fermentation to water. Hydrogen has been found to be a metabolite of Citrobacter, Cyanobacteria, Enterobacter, Halobacterium and Rhodobacteraceae (PMID: 28042989; PMID: 16371161) (https://www.insa.nic.in/writereaddata/UpLoadedFiles/PINSA/Vol51B_1985_2_Art16.pdf) (https://www.researchgate.net/publication/222428793_High_Hydrogen_Yield_from_a_Two-step_Process_of_Dark-_and_Photo-fermentation_of_Sucrose) (Tao, Y; Chen, Y; Wu, Y; He, Y; Zhou, Z (2007). "High hydrogen yield from a two-step process of dark- and photo-fermentation of sucrose". International Journal of Hydrogen Energy. 32 (2): 200-206). It is used as a packaging gas [DFC]

Trisulfur

S3 (95.916216)