Nickel is absorbed mainly through the lungs and gastrointestinal tract. Once in the body it enters the bloodstream, where it binds to albumin, L-histidine, and α2-macroglobulin. Nickel tends to accumulate in the lungs, thyroid, kidney, heart, and liver. Absorbed nickel is excreted in the urine, whereas unabsorbed nickel is excreted in the faeces. (L41)
Nickel is known to substitute for other essential elements in certain enzmes, such as calcineurin. It is genotoxic, and some nickel compounds have been shown to promote cell proliferation. Nickel has a high affinity for chromatin proteins, particularly histones and protamines. The complexing of nickel ions with heterochromatin results in a number of alterations including condensation, DNA hypermethylation, gene silencing, and inhibition of histone acetylation, which have been shown to disturb gene expression. Nickel has also been shown to alter several transcription factors, including hypoxia-inducible transcription factor, activating transcription factor, and NF-KB transcription factor. There is also evidence that nickel ions inhibit DNA repair, either by directly inhibiting DNA repair enzymes or competing with zinc ions for binding to zinc-finger DNA binding proteins, resulting in structural changes in DNA that prevent repair enzymes from binding. Nickel ions can also complex with a number of cellular ligands including amino acids, peptides, and proteins resulting in the generation of oxygen radicals, which induce base damage, DNA strand breaks, and DNA protein crosslinks. (L41, A40)
The most common harmful health effect of nickel in humans is an allergic reaction. This usually manifests as a skin rash, although some people experience asthma attacks. Long term inhahation of nickel causes chronic bronchitis and reduced lung function, as well as damage to the naval cavity. Ingestion of excess nickel results in damage to the stomach, blood, liver, kidneys, and immune system, as well as having adverse effects on reproduction and development. (L41)
Symptoms of nickel poisoning include headache, nausea, vomiting, dizziness, irritability, and difficulty sleeping, followed by chest pains, sweating, rapid heart beat, and a dry cough. (L42)
The biosynthetic pathway of coenzyme F430 in methanogenic and methanotrophic archaea
作者:Kaiyuan Zheng、Phong D. Ngo、Victoria L. Owens、Xue-peng Yang、Steven O. Mansoorabadi
DOI:10.1126/science.aag2947
日期:2016.10.21
biosynthesis of a nickel-containing tetrapyrrole coenzyme involves a series of five enzymes. Methyl-coenzyme M reductase (MCR) is the key enzyme of methanogenesis and anaerobic methane oxidation. The activity of MCR is dependent on the unique nickel-containing tetrapyrrole known as coenzyme F430. We used comparative genomics to identify the coenzyme F430 biosynthesis (cfb) genes and characterized the
Elucidation of the biosynthesis of the methane catalyst coenzyme F430
作者:Simon J. Moore、Sven T. Sowa、Christopher Schuchardt、Evelyne Deery、Andrew D. Lawrence、José Vazquez Ramos、Susan Billig、Claudia Birkemeyer、Peter T. Chivers、Mark J. Howard、Stephen E. J. Rigby、Gunhild Layer、Martin J. Warren
DOI:10.1038/nature21427
日期:2017.3.2
Methane biogenesis in methanogens is mediated by methyl-coenzyme M reductase, an enzyme that is also responsible for the utilization of methane through anaerobic methane oxidation. The enzyme uses an ancillary factor called coenzyme F430, a nickel-containing modified tetrapyrrole that promotes catalysis through a methyl radical/Ni(ii)-thiolate intermediate. However, it is unclear how coenzyme F430
产甲烷菌中的甲烷生物发生由甲基辅酶 M 还原酶介导,该酶还负责通过厌氧甲烷氧化利用甲烷。该酶使用称为辅酶 F430 的辅助因子,这是一种含镍改性四吡咯,可通过甲基自由基/Ni(ii)-硫醇盐中间体促进催化。然而,目前尚不清楚辅酶 F430 是如何从共同的始祖尿卟啉原 iii 合成的,将 11 个空间中心结合到大环中,尽管该途径必须涉及螯合、酰胺化、大环还原、内酰胺化和碳环形成。在这里,我们鉴定了催化辅酶 F430 从西罗氢氯酸中生物合成的蛋白质,称为 CfbA-CfbE,并证明了它们的活性。