Browsing Pathways

Hypermethioninemia is a rare error of metabolism (IEM) which arises when there is a disfunction in the gene called AHCY. This gene is responsible for Adenosylhomocysteinase, an enzyme which takes S-adenosyl homocysteine as input, and produces homocysteine as its output. This outputted compound through the its respective pathway may be turned back into cysteine methionine. A dysfunctional defect Adenosylhomocysteinase can lead to the build of of these two compounds in the blood. Of particular interest is that individuals who are affected by hypermethioninemia present a wide spectrum of symptoms. This ranges anywhere from the complete absence of symptoms, to mental retardation, muscle weakness, liver problems, and unusual facial features.

Hypermethioninemia is a rare error of metabolism (IEM) which arises when there is a disfunction in the gene called AHCY. This gene is responsible for Adenosylhomocysteinase, an enzyme which takes S-adenosyl homocysteine as input, and produces homocysteine as its output. This outputted compound through the its respective pathway may be turned back into cysteine methionine. A dysfunctional defect Adenosylhomocysteinase can lead to the build of of these two compounds in the blood. Of particular interest is that individuals who are affected by hypermethioninemia present a wide spectrum of symptoms. This ranges anywhere from the complete absence of symptoms, to mental retardation, muscle weakness, liver problems, and unusual facial features.

Hyperornithinemia with gyrate atrophy (HOGA), also known as gyrate atrophy of the choroid and retina, OAT deficiency, ornithine aminotransferase deficiency, ornithine keto acid aminotransferase deficiency) is an autosomal recessive disorder of ornithine metabolism caused by a defective ornithine aminotransferase (OAT). OAT catalyzes the conversion of ornithine into proline which is a conditionally essential amino acid. This disease is characterized by a very large accumulation of ornithine in the blood, urine, spinal fluid, and aqueous humour. Symptoms of the disease include early cataract formation, progressive chorioretinal degeneration, and type II muscle fiber atrophy. Some cases of HOGA are vitamin B6-responsive.

Hyperornithinemia with gyrate atrophy (HOGA), also known as gyrate atrophy of the choroid and retina, OAT deficiency, ornithine aminotransferase deficiency, ornithine keto acid aminotransferase deficiency) is an autosomal recessive disorder of ornithine metabolism caused by a defective ornithine aminotransferase (OAT). OAT catalyzes the conversion of ornithine into proline which is a conditionally essential amino acid. This disease is characterized by a very large accumulation of ornithine in the blood, urine, spinal fluid, and aqueous humour. Symptoms of the disease include early cataract formation, progressive chorioretinal degeneration, and type II muscle fiber atrophy. Some cases of HOGA are vitamin B6-responsive.

Hyperornithinemia-hyperammonemia-homocitrullinuria (HHH) syndrome is an autosomal recessive disorder of the urea cycle caused by a defective SLC25A15 gene. SLC25A15 codes for the mitochondrial ornithine carrier (ORC1) which transports ornithine between the cytoplasm and the mitochondrial matrix. This disease is characterized by a large accumulation of homocitrulline in the urine. Symptoms of the disease include mental retardation, spastic paraparesis, and myoclonic seizures associated with hyperornithinemia, hyperammonemia, and homocitrullinemia. Ornithine supplementation and restricted protein intake appear to be useful in the treatment of HHH syndrome.

Hyperornithinemia-hyperammonemia-homocitrullinuria (HHH) syndrome is an autosomal recessive disorder of the urea cycle caused by a defective SLC25A15 gene. SLC25A15 codes for the mitochondrial ornithine carrier (ORC1) which transports ornithine between the cytoplasm and the mitochondrial matrix. This disease is characterized by a large accumulation of homocitrulline in the urine. Symptoms of the disease include mental retardation, spastic paraparesis, and myoclonic seizures associated with hyperornithinemia, hyperammonemia, and homocitrullinemia. Ornithine supplementation and restricted protein intake appear to be useful in the treatment of HHH syndrome.

BH4-deficient hyperphenylalaninemia has several causes. One such cause is a PTS deficiency resultant from a genetic mutation. (In particular, a mutation in the gene encoding 6-pyruvoyl-tetrahydropterin synthase.) The mutation is autosomal recessive. Common symptoms include: muscular hypotonia, ataxia, bradykinesia, choreoathetosis, depressivity, dysphagia, hyperkinesis, hypsarrhythmia, myoclonus, and others. BH4 is a cofactor involved in many things and associated with neurotransmitter synthesis. In short, the reduction of levels of BH4 creates issues in the metabolism of phenylalanine. This cascade of reactions produces the aforementioned symptoms.

BH4-deficient hyperphenylalaninemia has several causes. One such cause is a PTS deficiency resultant from a genetic mutation. (In particular, a mutation in the gene encoding 6-pyruvoyl-tetrahydropterin synthase.) The mutation is autosomal recessive. Common symptoms include: muscular hypotonia, ataxia, bradykinesia, choreoathetosis, depressivity, dysphagia, hyperkinesis, hypsarrhythmia, myoclonus, and others. BH4 is a cofactor involved in many things and associated with neurotransmitter synthesis. In short, the reduction of levels of BH4 creates issues in the metabolism of phenylalanine. This cascade of reactions produces the aforementioned symptoms.

Hyperphenylalaninemia due to dihydropteridine reductase deficiency (DHPR) is the high presence of phenylalanine in the system/blood caused by a genetic mutation. More specificially, mutations in the QDPR gene are the root cause of the condition. One observes that such a mutation results in an error encoding a reductase enzyme, and from there a chain reaction of effects lead to the observed effects of the disease. The mutation is autosomal recessive. When tetrahydrobiopterin levels drop, the breakdown of many several amino acids, such as phenylalanine, is reduced and as a result their levels in the blood augment. Symptoms of hyperphenylalaninemia due to dihydropteridine reductase deficiency include: dysphagia, global development delay, microcephaly, and intellectual disability (among others). Treatment consists of BH4 supplements as well as other medical treatments.

Hyperphenylalaninemia due to dihydropteridine reductase deficiency (DHPR) is the high presence of phenylalanine in the system/blood caused by a genetic mutation. More specificially, mutations in the QDPR gene are the root cause of the condition. One observes that such a mutation results in an error encoding a reductase enzyme, and from there a chain reaction of effects lead to the observed effects of the disease. The mutation is autosomal recessive. When tetrahydrobiopterin levels drop, the breakdown of many several amino acids, such as phenylalanine, is reduced and as a result their levels in the blood augment. Symptoms of hyperphenylalaninemia due to dihydropteridine reductase deficiency include: dysphagia, global development delay, microcephaly, and intellectual disability (among others). Treatment consists of BH4 supplements as well as other medical treatments.