- Reduction of bound Hcy to free Hcy condensed
with an excess of serine to form cystathionine catalyzed by cystathionine β-synthase (CBS) - Hcy regeneration from cystathionine catalyzed
by cystathionine β-lyase (CBL) which releases
ammonia and pyruvate directly proportional to Hcy - Pyruvate is measured at 340 nm using LDH
and NADH
What is Homocysteine?
Homocysteine is an amino acid in the blood. Epidemiological studies have shown that too much homocysteine in the blood is related to a higher risk of coronary heart disease, stroke and peripheral vascular disease.
Other evidence suggests that homocysteine may have an effect on atherosclerosis by damaging the inner lining of arteries and promoting blood clots. However, a direct causal link hasn’t been established.
Diet and Genetic Factors
Plasma homocysteine levels are strongly influenced by diet, as well as by genetic factors. The dietary components with the greatest effects are folic acid and vitamins B6 and B12. Folic acid and other B vitamins help break down homocysteine in the body. Several studies have found that higher blood levels of B vitamins are related, at least partly, to lower concentrations of homocysteine. Other recent evidence shows that low blood levels of folic acid are linked with a higher risk of fatal coronary heart disease and stroke.
Current Research
Several clinical trials are under way to test whether lowering homocysteine will reduce CHD risk. Recent data show that the institution of folate fortification of foods has reduced the average level of homocysteine in the U.S. population.
Importance of Homocysteine Testing
Recent findings suggest that laboratory testing for plasma homocysteine levels can improve the assessment of risk. It may be particularly useful in patients with a personal or family history of cardiovascular disease, but in whom the well-established risk factors (smoking, high blood cholesterol, high blood pressure) do not exist.
© 2008 American Heart Association, Inc.