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首页> 外文期刊>Indian Journal of Biochemistry & Biophysics >Biochemistry of homocysteine in health and diseases
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Biochemistry of homocysteine in health and diseases

机译:同型半胱氨酸在健康和疾病中的生物化学

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摘要

The amino acid homocysteine (Hey), formed from methionille has profound importance in health and diseases. In normal circtlmstmtces. it is converted to cysteine and partly remethylated to methionine with the help of vit B-12 and folate. However, when normal metabolism is disturbed, due to deficiency of cystathionine-beta-synthase, which requires vit B-6 for activation. Hcy is accumulated in the blood with an increase of methionine, resulting into mental retardation (homocystinuria type I). A decrease of cysteine may cause eye diseases, due to decrease in the synthesis of glutathione (antioxidant). In homocystinurias type II, III and IV, there is accumulation of Hey, but a decrease of methionine, thus, there is no mental retardation. I-Iomocysteinemia is found in Marfan syndrome, some cases of type I diabetes and is also linked to smoking and has genetic basis too. In hyperhomocysteinemias (HHcys), clinical manifestations are mental retardation and seizures (type I only), ectopia lentis, secondary glaucoma, optic atrophy, retinal detachment, skeletal abnormalities, osteoporosis, vascular changes, neurological dysfunction and psychiatric symptoms. Thrombotic and cardiovascular diseases may also be encountered. The harmful effects of homocysteinemias are due to (i) production of oxidants (reactive oxygen species) generated during oxidation of I-Icy to homocystine and disulphides in the blood. These could oxidize membrane lipids and proteins, (ii) Hcy can react with proteins with their thiols and form disulphides (thiolation); (iii) it can also be converted to highly reactive thiolactone which could react with the proteins forming -NH-CO- adducts, thus affecting. the body proteins and enzymes. Honocystinuria type I is very rare (1 in 12 lakhs only) and is treated with supplementation of vit B-6 and cystine. Others are more common and are treated with folate, vit B-6 and in selected cases as in, methionine svnthase deficiency. methionine, avoiding excess. In this review, the role of' elevated Hey levels in cardiovascular, ocular, nettrologial and other diseases and the possible therapeutic measures, in addition to the molecular mechanisms involved in deleterious manifestations of ltomocysteinemia, have been discussed.
机译:由甲硫氨酸形成的氨基酸高半胱氨酸(Hey)在健康和疾病中具有重要意义。在正常情况下。借助vit B-12和叶酸将其转化为半胱氨酸并部分重新甲基化为蛋氨酸。但是,当正常代谢受到干扰时,由于缺乏胱硫醚-β-合酶,需要激活vit B-6。 Hcy随着蛋氨酸的增加而积累在血液中,导致智力低下(I型高胱氨酸尿症)。由于谷胱甘肽(抗氧化剂)的合成减少,半胱氨酸的减少可能会引起眼部疾病。在II,III和IV型高半胱氨酸尿症中,有Hey的积累,但是蛋氨酸的减少,因此,没有智力障碍。 I-同型半胱氨酸血症存在于Marfan综合征(某些I型糖尿病病例)中,也与吸烟有关,也具有遗传基础。在高同型半胱氨酸血症(HHcys)中,临床表现为智力低下和癫痫发作(仅I型),轻度ectopia,继发性青光眼,视神经萎缩,视网膜脱离,骨骼异常,骨质疏松,血管变化,神经功能障碍和精神病性症状。也可能遇到血栓和心血管疾病。高半胱氨酸血症的有害影响是由于(i)在I-Icy氧化为血液中的高半胱氨酸和二硫化物期间产生的氧化剂(活性氧)产生。这些可以氧化膜脂质和蛋白质,(ii)Hcy可以与蛋白质及其硫醇反应形成二硫化物(硫醇化); (iii)它也可以转化为高反应性的硫代内酯,其可以与形成-NH-CO-加合物的蛋白质反应,从而产生影响。体内的蛋白质和酶。 I型高半胱氨酸尿症非常罕见(仅每120万例中有1例),并补充了维生素B-6和胱氨酸治疗。其他一些则更常见,并用叶酸,vit B-6进行治疗,在某些情况下,如甲硫氨酸合酶缺乏症。蛋氨酸,避免过量。在这篇综述中,已经讨论了升高的Hey水平在心血管,眼病,内分泌疾病和其他疾病中的作用以及可能的治疗措施,以及涉及半胱氨酸血症有害表现的分子机制。

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