There is much investigation today into the relationship
of elevated homocysteine and cardiovascular disease.
Homocysteinemia is widely associated with cardiovascular
disease in the form of
atherosclerosis,
myocardial infarction,
peripheral arterial disease, venous thrombosis, hyperten-
sion, and cerebrovascular
disease.
Considerable speculation
exists to the adverse effects of elevated homocysteine and
neural tube defects, colorectal cancer, and dementia. This
research paper is an attempt to explore homocysteinemia as
a causative.agent; in cerebrovascular disease and stroke.
Homocysteine has the molecular formula
HSCH2CH2CH(NH2)CO2H. Homocysteine cannot be
obtained through the diet. It is made from the amino acid
methionine by the removal of its terminal methyl group.
Homocysteine can be regenerated into methionine or con-
verted into cysteine through the utilization of folie acid and
vitamin B12. Homocysteine is similar to the amino acid
cysteine but differs in that it has one additional méthylène
group.
Elevated homocyteine in the blood is termed homo-
cyteinemia and in the urine, homocysteinuria.
Homocysteine is currently utilized as a laboratory marker
of cardiovascular heart disease such as stroke, atherosclero-
sis,
CVD, and hypertension. This cardiovascular disease
risk has been documented to be readily remedied with folie
acid therapy. Homocysteine is methylated to methionine
by the transfer of the methyl group of methylenetetrahy-
drofo (MTHF). Methylenetetrahydrofolate is made by the
reduction of a méthylène group. The reduction of methyl-
ene of methyle- netetrahydrofolate is catalyzed by
methylenetetrahydrofolate reductase enzyme.' In this
remethylation process of homocysteine, 5MTHF and
methylcobalamin form a prosthetic group for the enzyme
methionine synthase. Methylcobalamin is the methyl donor
necessary to make homocysteine into methionine. Con-
versely, methionine is converted to homocystiene in the
following mechanism. Methionine is converted to S-adeno-
sylmethionine (SAM) catalyzed by methionine adenosyl
transferase. The methyl group is taken from SAM to form
S-adenosyl
homocysteine (SAH). When the adenosyl
group is taken from SAH, homocysteine is formed.
MTHFR enzyme normally converts dietary folate into its