Homocysteine - a molecule attracting increasing attention

In the last 30 years, homocysteine has been the subject of medical and bioc hemical research as an indicator. Its concentration in body fluids indicate s the hereditary disorder, homocystenuria, and arteriosclerosis and cardiov ascular diseases in general. On the basis of improved methods of homocystei ne determination in blood, different levels of homocysteinemia can now be d istinguished indicating different kinds of diseases which require different medical treatment. In the newly outlined metabolic reaction schemes in thi s paper, homocysteine appears as an intermediate in several vitally importa nt interconnected cycles. Under normal physiological conditions, Its plasma concentration remains within standard limits, while its increase signals d ysfunction of some of the essential pathways affecting membrane transport, redox and pH equilibria and energy production in the organism. In these con certed metabolic processes S-adenosylmethionine, folates and vitamins Bg an d Bit as well as NO play important roles.