Homocystein enzymatic

产品名称：Homocystein enzymatic
产    地：Demeditec 
产品货号：DE568A
产品规格：185 Tests
产品说明：
Special remarks: This enzymatic Homocystein test can be performed on the following clinical chemistry analyzers:
- Cobas Mira
- Hitachi 717, 911, 917
- Synchron-CX-7
- Olympus AU400
- Dimension AR
- Aeroset
- Advia 1650
- Modular P
Adaption protocols are available for each of the a.m. instruments.
Separate control sets are available upon request:
 - 2-level control containing 2x3 ml  concentrations 7 - 29 pMol/ml
 - 4-level control containing 4x3 ml  concentrations 7 - 12 - 29 - 40 pMol/ml
Background information
Homocysteine is a chemical compound with the formula HSCH2-CH2-CH(NH2)-COOH. It is a homologue of the naturally-occurring amino acid cysteine, differing in that its side-chain contains an additional methylene (-CH2-) group before the thiol (-SH) group. Alternatively, homocysteine can be derived from methionine by removing the latter's terminal Cε methyl group.
Organic chemical properties
The "extra" (relative to cysteine) one carbon methylene group allows this molecule to form a five-membered ring, homocysteine thiolactone. The facility of this reaction precludes the formation of stable peptide bonds. In other words, a protein containing homocysteine would tend to cleave itself.
The 4 carbon homocysteine is (only) made from the 5 carbon methionine, an essential amino acid, in a multi step reaction via S-adenosyl methionine. Homocysteine can be recycled back into methionine or it can be permanently converted to cysteine via the transsulfuration pathway. Homocysteine is not obtained from the diet; it is a normal temporary and chemically reactive reaction product that can be measured in blood. Due to its high reactivity to proteins, it is almost always bound to proteins, 'thiolating' (and thus degrading) most notably the lysine and cysteine components thereof. This can permanently affect protein function. In blood, it is found bound to albumin and to hemoglobin. It affects enzymes with cysteine-containing active sites, for example, it inhibits lysyl oxidase a key enzyme in the production of collagen and elastin, two main structural proteins in artery, bone and skin.
Elevated homocysteine
As a consequence of the biochemical reactions in which homocysteine is involved, deficiencies of the vitamins folic acid (B9), pyridoxine (B6), or B12 (cyanocobalamin) can lead to high homocysteine levels. Supplementation with pyridoxine, folic acid, B12 or trimethylglycine (betaine) reduces the concentration of homocysteine in the bloodstream. Increased levels of homocysteine are linked to high concentrations of endothelial asymmetric dimethylarginine.
Elevations of homocysteine also occur in the rare hereditary disease homocystinuria and in the methylene-tetrahydrofolate-reductase polymorphism genetic traits. The latter is quite common (about 10% of the world population) and it is linked to an increased incidence of thrombosis and cardiovascular disease and that occurs more often in people with above minimal levels of homocysteine (about 6 μmol/L). Common levels in Western populations are 10 to 12 and levels of 20 μmol/L are found in populations with low B-vitamin intakes (New Delhi) or in the older elderly (Rotterdam, Framingham). Women have 10-15% less homocysteine during their reproductive decades than men which may help explain the fact they suffer myocardial infarction (heart attacks) on average 10 to 15 years later than men.
Cardiovascular risks
A high level of blood serum homocysteine is a powerful risk factor for cardiovascular disease. Unfortunately attempts to decrease the risk by lowering homocysteine have not been fruitful.
Studies reported in 2006 have shown that giving vitamins [folic acid, B6 and B12] to reduce homocysteine levels may not quickly offer benefit, however a significant 25% reduction in stroke was found in the HOPE-2 study even in patients mostly with existing serious arterial decline although the overall death rate was not significantly changed by the intervention in the trial. Clearly, reducing homocysteine does not quickly repair existing structural damage of the artery architecture. However, the science is strong supporting the biochemistry that homocysteine degrades and inhibits the formation of the three main structural components of the artery, collagen, elastin and the proteoglycans. Homocysteine permanently degrades cysteine [disulfide bridges] and lysine amino acid residues in proteins, gradually affecting function and structure. Simply put, homocysteine is a 'corrosive' of long-living [collagen, elastin] or life-long proteins [fibrillin]. These long-term effects are difficult to establish in clinical trials focusing on groups with existing artery decline. The main role of reducing homocysteine is likely in 'prevention' but with a slow but probable role in 'cure'.
Bone weakness
Elevated levels of homocysteine have been linked to increased fractures in elderly persons. Homocysteine does not appear to have any effect on bone density. Instead, it appears that homocysteine affects collagen by interfering with the cross-linking between collagen fibers and the tissues they reinforce.
Vitamin supplements could counter the effects of homocysteine on collagen. As B12 is inefficiently absorbed from food by elderly persons, they could gain a greater benefit from taking in higher doses orally or via intramuscular injection.
上海玉博生物技术有限公司在为生命科学领域提供丰富的产品与信息资源方面处于国内**地位，公司提供的产品涵盖了二十多个国家近五十万种产品，而且产品的数量与信息在不断的增长和更新，公司提供的产品能够使生命科学工作者加快对生物化学，分子生物学，细胞生物学以及蛋白质组学研究的认知，以及分子诊断和临床医学领域的应用。

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