Introduction of homocysteine

Homocysteine, or homocysteine or homocysteine, is a heterologous amino acid cysteine that contains an additional methylene group (-SH) in the side chain portion of the thiol group (-CH2-).

The chemical properties of homocysteine

The extra methylene of homocysteine makes the thiol group closer to the carboxyl group, enabling it to initiate a chemical reaction to form a five-membered ring called the homocysteine thiolactone. This reaction occurs when the amino acid normally forms a peptide bond with its adjacent moiety. Homocysteine is not suitable for mixing with proteins, because homocysteine-containing proteins break down on their own.

Homocysteine is formed from S-adenosylmethionine through two reaction step pathways and can be converted to methionine or converted to cysteine or taurine via a sulfur transfer pathway. Although homocysteine can be converted to cysteine, there is no evidence that human direct consumption of homocysteine is converted to cysteine.

The biochemical mechanism of homocysteine

1969 Mccully autosomalic homocysteinuria death from autopsy found in the body circulation, there is a wide range of arterial thrombosis and atherosclerosis (AS) of the pathological manifestations, which proposed high homocysteine blood The hypothesis that hyperhomocysteinemia (HHCY) can lead to atherosclerotic vascular disease. Since then, scholars of various countries on the relationship between HCY and cardiovascular and cerebrovascular diseases have done a lot of research. Hcy is a mercapto-containing amino acids, mainly from dietary intake of methionine, methionine and cysteine metabolism is an important intermediate product, which itself does not participate in protein synthesis. In vivo, about 1/2 of the Hcy and methyltetrahydrofolate in methionine synthase (Methionine Synthase reductase, MS) under the action of methionine and tetrahydrofolic acid, tetrahydrofolic acid in the N5, N10-methylene tetrahydro (MTHFR). Methylenetetrahydrofolate (MTHFR) produced methyltetrahydrofolic acid. The other half of the Hcy was converted to Cystathionineβ-synthase (CBS) by the thiored pathway. Under the formation of cystathionine, part of cystathionine in the role of cysteine to form cysteine, and finally the formation of pyruvic acid, sulfuric acid and water, the process requires vitamin B6 as coenzyme and serine hydroxymethyl transferase, the other part is generated Homologous serine. Any cause of the first two metabolic pathways, elevated Hcy in the aminoacyl-tRNA synthetase under the action of the formation of homocysteine thiolactone (homocysteine thiolactone, HTL), HTL is Hcy in aminoacyl-tRNA Synthetic enzyme editing or correction process in the formation of reaction products, is a cyclothiolate. Hcy can directly or indirectly lead to vascular endothelial cell injury, promote vascular smooth muscle cell proliferation, low-density lipoprotein oxidation, enhance platelet function, promote thrombosis.

Determination of homocysteine

The first detection of homocysteine is amino acid analysis, Ueland and other determination of serum homocysteine, after improved, the commonly used methods include the following.

Isotope method: established by Refsum et al. 1985. In this method, the HCY concentration was determined by chromatographic separation and liquid scintillation counting of radioactivity after 14C-labeled adenosine was condensed with HCY. This method has high sensitivity and specificity, but it is complicated and radioactive pollution, and can not be popularized.

Chromatography: In 1987 Stabler first reported the determination of homocysteine by gas chromatography-mass spectrometry. The method can simultaneously determine cysteine, methionine, cystathionine and methyl glycine and other substances. Although the sensitivity, specificity is good, but the instrument is expensive and can not promote. High performance liquid chromatography (HPLC) is a relatively mature and widely used method. The disadvantage is that sample processing, chromatographic conditions, sample detection and quantification of many variations, making it difficult to standardize. Fiskertrand and other first in 1993 with automatic high-performance liquid chromatography on plasma and urine HCY and thiol substances were determined. HPLC can be divided into a variety of methods depending on the derivatization method (pre-column or post-column derivatization), detection method (fluorescence, electrochemistry). Application of HPLC for accurate determination of homocysteine requires excellent equipment, superb technical experience and the appropriate time to apply HPLC method, and the selection and preparation of internal quality control is also very important.

Immunoassay: The method uses a specific anti-S-adenosine homocysteine monoclonal technology, the fluorescence polarization method or immunoassay for the determination of HCY. Abbott US companies use fully automated fluorescence polarization immunoassay technology, with AXSYM instrument detection HCY , The reaction principle is: normal human plasma HCY about 1% to reduce the type of existence, 70% and albumin binding, 30% of the formation of small molecules disulfide. HCY, mixed disulfide and protein binding, etc., were reduced to free HCY form (tHCY) in the presence of dithiothreitol-containing pretreatment solution: tHCY in the S-adenosyl-L-isotype half Cysteine (SAH) hydrolase and excess adenosine in the presence of SAH; a pre-diluted SAH mixture, an anti-SAH monoclonal antibody and a labeled fluorescent S-adenosyl-L-cysteine tracer Together, the instrument automatically detects changes in polarized light, you can measure the total sample HCY level. This method is fast, easy to operate, high degree of automation, can reduce human error, with good accuracy and precision, suitable for most clinical laboratory applications.

The role of homocysteine

Homocysteine is an important amino acid in the body of methionine conversion. Because meat, cheese and other protein foods are particularly rich in methionine content, so we almost every day to eat this methionine. The level of homocysteine in our body is known as the H value (H Score), H value can more accurately predict the risk of heart disease or stroke, and better than the gene to predict the risk of Alzheimer's disease. In fact, H values can help predict nearly 50 disease risks, including all causes of premature death. It can even tell you the current rate of aging. By reflecting the nutritional status of vitamin B, the immune system function and brain conditions, can show the body's chemical status is normal.

The lower the homocysteine concentration is, the more perfect your body will be able to maintain a perfect biochemical balance. This means more energy, better endurance and endurance, a sober mind, less infection and better skin and weight control. Therefore, if you do not maintain a homocysteine concentration lower or within the equilibrium range, you will encounter the following ten questions:

1. To accelerate oxidation and aging

2. Damage your arteries

3. Weaken the immune system

4. Damage to the brain and reduce IQ

5. increase pain, inflammation and thrombosis

6. susceptible to cancer and detoxification problems

7. Accelerates aging of the brain

8. Hormonal problems

9. Vitamin B deficiency

10. The lack of SAMe

Therefore, homocysteine is an important health indicators.

Synthesis and degradation of homocysteine

When we exercise or only a slight movement, our liver will produce creatine to help muscle contraction. One of the by-products of creatine is homocysteine. Homocysteine is harmful in the body, need to be excluded in order to maintain the health of the body. In this sense, a long period of exercise a large amount of exercise is harmful to the body.

Our body has several ways to degrade homocysteine in the body. One approach is through the recovery of methionine via. Because homocysteine in the body is produced by methionine. By "where it comes from, where to return," the method can be effective in reducing the concentration of homocysteine in the body. We must have enough folic acid and vitamin B-12 in our body to keep the recycling work done well. Second, homocysteine can be converted to cysteine in the presence of vitamin B-6. There is another way, by adding creatine (creatine) to reduce the creatine in the body, thereby reducing the production of homocysteine in the body.