NISCAIR Online Periodicals Repository

NISCAIR ONLINE PERIODICALS REPOSITORY (NOPR)  >
NISCAIR PUBLICATIONS >
Research Journals >
Indian Journal of Biochemistry and Biophysics (IJBB) >
IJBB Vol.43 [2006] >
IJBB Vol.43(5) [October 2006] >


Title: Biochemistry of homocysteine in health and diseases
Authors: Ramakrishnan, S
Sulochana, K N
Lakshmi, S
Selvi, R
Angayarkanni, N
Keywords: Homocysteine metabolism
Homocystinurias
Homocysteinemias
Clinical manifestations
Thrombotic disorders
Cardiovascular diseases
Diabetes
Ocular diseases
Smokers
Oxidant stress
Protein thiolation
Protein homocysteinylation
Cystine
Vitamins B6
B12
folate
Issue Date: 2006
Publisher: CSIR
Abstract: The amino acid homocysteine (Hcy), formed from methionine has profound importance in health and diseases. In normal circumstances, it is converted to cysteine and partly remethylated to methionine with the help of vit B12 and folate. However, when normal metabolism is disturbed, due to deficiency of cystathionine-b-synthase, which requires vit B6 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 Hcy, but a decrease of methionine, thus, there is no mental retardation. Homocysteinemia 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 Hcy 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. Homocystinuria type I is very rare (1 in 12 lakhs only) and is treated with supplementation of vit B6 and cystine. Others are more common and are treated with folate, vit B12 and in selected cases as in methionine synthase deficiency, methionine, avoiding excess. In this review, the role of elevated Hcy levels in cardiovascular, ocular, neurologial and other diseases and the possible therapeutic measures, in addition to the molecular mechanisms involved in deleterious manifestations of homocysteinemia, have been discussed.
Page(s): 275-283
ISSN: 0301-1208
Source:IJBB Vol.43(5) [October 2006]

Files in This Item:

File Description SizeFormat
IJBB 43(5) 275-283.pdf290.62 kBAdobe PDFView/Open
 Current Page Visits: 1086 
Recommend this item

 

National Knowledge Resources Consortium |  NISCAIR Website |  Contact us |  Feedback

Disclaimer: NISCAIR assumes no responsibility for the statements and opinions advanced by contributors. The editorial staff in its work of examining papers received for publication is helped, in an honorary capacity, by many distinguished engineers and scientists.

CC License Except where otherwise noted, the Articles on this site are licensed under Creative Commons License: CC Attribution-Noncommercial-No Derivative Works 2.5 India

Copyright © 2012 The Council of Scientific and Industrial Research, New Delhi. All rights reserved.

Powered by DSpace Copyright © 2002-2007 MIT and Hewlett-Packard | Compliant to OAI-PMH V 2.0

Home Page Total Visits: 556476 since 06-Feb-2009  Last updated on 15-Jul-2014Webmaster: nopr@niscair.res.in