Browsing Pathways

Prolinemia Type II is caused by mutation in the pyrroline-5-carboxylate dehydrogenase gene (P5CDH) mitochondrial matrix NAD-dependent dehydrogenase. This dehydrogenase is a catalyst for converting pyrroline-5-carboxylate to glutamate in the proline degradation pathway. An enzyme defect causes accumulation of glycine, hydroxyproline and proline in the urine, ornithine in the serum and proline in plasma. Symptoms include mental retardation, acute and chronic renal failure, and seizures.

Prolidase deficiency is an autosomal recessive disorder. The enzyme prolidase cleaves iminodipeptides with N-terminal proline or hydroxyproline. Collagen has high levels of iminoacids therefore, these dipeptidases are important for collagen metabolism. A defect in this enzyme causes accumulation of imidodipeptides in urine. Symptoms include skin lesions, anemia, dysmorphism, mental retardation, and ptosis (drooping eyelid).

Phenylketonuria, also called Folling disease, is a rare inborn error of metabolism (IEM) and autosomal recessive disorder that affects the proper processing of phenylalanine caused by a defective phenylalanine hydroxylase. Phenylalanine hydroxylase breaks down phenylalanine from the diet. This disorder is characterized by a large accumulation of phenylalanine in the blood and other tissues. Symptoms of the disorder include behavioural problems, psychiatric disorders and seizures. Treatment eating a diet limiting the intake of phenylalanine is very effective. It is estimated that phenylketonuria affects 1 in 15,000 individuals in the United States.

Ornithine transcarbamylase deficiency (OTC deficiency), is a rare inborn error of metabolism (IEM) and X-linked disorder of the urea cycle caused by a deficiency of ornithine transcarbamylase. Ornithine transcarbamylase is responsible for processing nitrogen produced by the urea cycle. This disorder is characterized by a large accumulation of ammonia in the bloodstream. Symptoms of the disorder include lethargy, seizures, or coma. Treatment with hemodialysis is very effective in patients with high ammonia blood levels. It is estimated that ornithine transcarbamylase deficiency affects 1 in 14,000 to 1 in 77,000 individuals. These estimates are very different because adults with the late-onset form of ornithine transcarbamylase deficiency are less likely to come to medical attention.

Molybdenium cofactor deficiency (Sulfite oxidase deficiency) is caused by mutations in the genes MOCS1 and MOCS2 in the formation of molybdenum cofactor. A molybdenum-containing cofactor is essential to the function of 3 enzymes: sulfite oxidase, xanthine dehydrogenase, and aldehyde oxidase. Xanthine dehydrogenase is a molybdenum-containing hydroxylase involved in the oxidative metabolism of purines. Defects in this enzyme cause accumulation of hypoxanthine,, s-s-sulfocysteine, taurine, and xanthine in the urine. Symptoms include hemorrhage, cerebral atrophy, encephalopathy, lactic acidosis, nystagmus, spastic diplegia/quadriplegia, and vomiting.

Myoneurogastrointestinal encephalopathy, or mitochondrial neurogastrointestinal encephalopathy syndrome (MNGIE), is a multisystem disorder caused by mutations in the gene encoding thymidine phosphorylase, which normally uses thymidine and phosphate as substrates to catalyze the reaction between these two substrates to create thymine and 2-deoxy-alpha-D-ribose 1-phosphate. MNGIE causes accumulation of thymidine and deoxyuridine in the urine. Symptoms of MNGIE include ptosis, progressive external ophthalmoplegia, gastrointestinal dysmotility (often pseudoobstruction), diffuse leukoencephalopathy, peripheral neuropathy, and myopathy.

Methylcobalamin (MeCbl) is the cofactor of methionine synthase and involved in the conversion of homocysteine to methionine. Adenosylcobalamin (AdoCbl) is a cofactor for methylmalonyl CoA mutase converting methylmalonic acid into succinic acid. Methylmalonyl-CoA mutase is involved in key metabolic pathways, catalyzing the isomerization of methylmalonyl-CoA to succinyl-CoA. It requires its Vitamin B12 derived prosthetic group, adenosylcobalamin, to function.It catalyzes the isomerization of methylmalonyl-CoA to succinyl-CoA. It requires its Vitamin B12 derived prosthetic group, adenosylcobalamin, to function. Defects in these cofactors for methylmalonyl CoA mutase cause accumulation of ammonia in blood; methylmalonic acid in plasma; creatinine and uric acid in serum; 3-Aminoisobutyric acid, 3-Hydroxypropionic acid, 3-Hydroxyvaleric acid, glycine, methylcitric acid and methylmalonic acid in urine; and methylmalonic acid in spinal fluid. Symptoms include anemia, dehydration, growth retardation, nephrosis, respiratory distress and metabolic acidosis.

Methylmalonic acidemia cause defects (Methylmalonaciduria due to methylmalonic CoA mutase; Acidemia, methylmalonic; MMA) in the metabolic pathway where methylmalonyl-coenzyme A (CoA) is converted into succinyl-CoA by the enzyme methylmalonyl-CoA mutase. Defects in the enzyme Methylmalonyl-CoA mutase causes accumulation of ammonia in blood; methylmalonic acid in plasma; creatinine and uric acid in serum; 3-Aminoisobutyric acid, 3-Hydroxypropionic acid, 3-Hydroxyvaleric acid, glycine, methylcitric acid and methylmalonic acid in urine; and methylmalonic acid in spinal fluid. Symptoms include anemia, dehydration, growth retardation, nephrosis, respiratory distress and metabolic acidosis.

Maple syrup urine disease, also called BCKD deficiency, is a rare inborn error of metabolism (IEM) and autosomal recessive disorder caused by a defective BCKDHA, BKCDHB or DBT gene. These genes code for a protein which is vital in the breakdown of amino acids, specifically the amino acids leucine, isoleucine and valine. This disorder is characterized by a large accumulation of these amino acids in the body. Symptoms of the disorder include a distinct maple syrup smell of the urine, vomiting, lethargy, abnormal movements and delayed development. Treatment includes long-term dietary management which aims to restrict the consumption of branched-chain amino acids. It is estimated that maple syrup urine disorder affects 1 in 185,000 infants globally. This number increases significantly when looking specifically at Old World Order Mennonites, where the prevalence is 1 in 380 infants.

Malonyl-CoA decarboxylase deficiency, also called malonic aciduria, is a rare inborn error of metabolism (IEM) and autosomal recessive disorder caused by a defective MLYCD gene. The MLYCD gene codes for the protein malonyl-CoA decarboxylase which regulates the creation and degradation of fatty acids. This disorder is characterized by a large accumulation of fatty acid byproducts in the tissues. Symptoms of the disorder include delayed development, hypotonia, seizures, vomiting, diarrhea and cardiomyopathy. Treatment with L-carnitine is very effective, as it encourages beta-oxidation of fatty acids. Less than 30 cases globally have ever been reported, making this disorder extremely rare.