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Homocystinuria (HCU) [2] is an inherited disorder of the metabolism of the amino acid methionine due to a deficiency of cystathionine beta synthase or methionine synthase. [3] It is an inherited autosomal recessive trait, which means a child needs to inherit a copy of the defective gene from both parents to be affected.
Cystathionine beta synthase (CBS) is involved in oocyte development. However, little is known about the regional and cellular expression patterns of CBS in the ovary and research is now focused on determining the location and expression during follicle development in the ovaries.
Homocystinuria is the second most common cause of heritable ectopia lentis. Homocystinuria is an autosomal recessive metabolic disorder most often caused by a near absence of cystathionine b-synthetase. It is associated with intellectual disability, osteoporosis, chest deformities, and increased risk of thrombotic episodes.
Cystathionine is an intermediate in the synthesis of cysteine from homocysteine. It is produced by the transsulfuration pathway and is converted into cysteine by cystathionine gamma-lyase (CTH). Biosynthetically, cystathionine is generated from homocysteine and serine by cystathionine beta synthase (upper reaction in the diagram below).
Cystathioninuria, also called cystathionase deficiency, is an autosomal recessive [1] metabolic disorder. It is characterized by an abnormal accumulation of plasma cystathionine leading to excess cystathionine in the urine. Hereditary cystathioninuria is associated with the reduced activity of the enzyme cystathionine gamma-lyase. [2]
Inborn errors of metabolism form a large class of genetic diseases involving congenital disorders of enzyme activities. [1] The majority are due to defects of single genes that code for enzymes that facilitate conversion of various substances into others ().
Reaction 5 is catalyzed by cystathionine beta-synthase while reaction 6 is catalyzed by cystathionine gamma-lyase. The required homocysteine is synthesized from methionine in reactions 1, 2, and 3. The transsulfuration pathway is a metabolic pathway involving the interconversion of cysteine and homocysteine through the intermediate cystathionine.
High levels of homocysteine in the blood (hyperhomocysteinemia) is regarded as a marker of cardiovascular disease, likely working through atherogenesis, which can result in ischemic injury. Therefore, hyperhomocysteinemia is a possible risk factor for coronary artery disease .