Pathways

Carnitine palmitoyltransferase I deficiency, which is also known as CPT I deficiency, is a very rare inherited inborn error of metabolism (IEM) leading to muscle weakness. Fewer than 50 people have been identified with this condition. It is an autosomal recessive disorder associated with a mutation in the enzyme carnitine palmitoyltransferase I. Carnitine palmitoyltransferase I (CPT1) is also known as carnitine acyltransferase I (CAT1), CoA:carnitine acyl transferase (CCAT), or palmitoylCoA transferase I. CPT I is a mitochondrial enzyme. It is responsible for the formation of acylcarnitines by catalyzing the transfer of the acyl group of a long-chain fatty acyl-CoA from CoA to carnitine. Carnitine, a natural substance acquired mostly through the diet, is used by cells to process fats and produce energy. Defects in CPT I prevents the body from using certain fats for energy, particularly during periods of fasting. Affected individuals often have increased carnitine levels along with low blood sugar (hypoglycemia) and a low level of ketones (hypoketosis), which are produced during fat metabolism as an energy source. Together these signs are termed hypoketotic hypoglycemia. The condition's severity varies greatly among affected individuals and many of the signs and symptoms manifest during early childhood. People with CPT I deficiency can also have an enlarged liver (hepatomegaly) and liver malfunction. CPT I deficienct individuals are at risk for liver failure, nervous system damage, seizures, coma, and sudden death. Affected individuals should eat a high-carbohydrate, low-fat diet and avoid fasting.

Carnitine palmitoyltransferase I deficiency, which is also known as CPT I deficiency, is a very rare inherited inborn error of metabolism (IEM) leading to muscle weakness. Fewer than 50 people have been identified with this condition. It is an autosomal recessive disorder associated with a mutation in the enzyme carnitine palmitoyltransferase I. Carnitine palmitoyltransferase I (CPT1) is also known as carnitine acyltransferase I (CAT1), CoA:carnitine acyl transferase (CCAT), or palmitoylCoA transferase I. CPT I is a mitochondrial enzyme. It is responsible for the formation of acylcarnitines by catalyzing the transfer of the acyl group of a long-chain fatty acyl-CoA from CoA to carnitine. Carnitine, a natural substance acquired mostly through the diet, is used by cells to process fats and produce energy. Defects in CPT I prevents the body from using certain fats for energy, particularly during periods of fasting. Affected individuals often have increased carnitine levels along with low blood sugar (hypoglycemia) and a low level of ketones (hypoketosis), which are produced during fat metabolism as an energy source. Together these signs are termed hypoketotic hypoglycemia. The condition's severity varies greatly among affected individuals and many of the signs and symptoms manifest during early childhood. People with CPT I deficiency can also have an enlarged liver (hepatomegaly) and liver malfunction. CPT I deficienct individuals are at risk for liver failure, nervous system damage, seizures, coma, and sudden death. Affected individuals should eat a high-carbohydrate, low-fat diet and avoid fasting.

Carnitine palmitoyltransferase I deficiency, which is also known as CPT I deficiency, is a very rare inherited inborn error of metabolism (IEM) leading to muscle weakness. Fewer than 50 people have been identified with this condition. It is an autosomal recessive disorder associated with a mutation in the enzyme carnitine palmitoyltransferase I. Carnitine palmitoyltransferase I (CPT1) is also known as carnitine acyltransferase I (CAT1), CoA:carnitine acyl transferase (CCAT), or palmitoylCoA transferase I. CPT I is a mitochondrial enzyme. It is responsible for the formation of acylcarnitines by catalyzing the transfer of the acyl group of a long-chain fatty acyl-CoA from CoA to carnitine. Carnitine, a natural substance acquired mostly through the diet, is used by cells to process fats and produce energy. Defects in CPT I prevents the body from using certain fats for energy, particularly during periods of fasting. Affected individuals often have increased carnitine levels along with low blood sugar (hypoglycemia) and a low level of ketones (hypoketosis), which are produced during fat metabolism as an energy source. Together these signs are termed hypoketotic hypoglycemia. The condition's severity varies greatly among affected individuals and many of the signs and symptoms manifest during early childhood. People with CPT I deficiency can also have an enlarged liver (hepatomegaly) and liver malfunction. CPT I deficienct individuals are at risk for liver failure, nervous system damage, seizures, coma, and sudden death. Affected individuals should eat a high-carbohydrate, low-fat diet and avoid fasting.

Carnitine palmitoyltransferase II deficiency, which is also known as CPT II deficiency, is an inherited inborn error of metabolism (IEM) of fatty acid oxidation leading to muscle weakness. It is the most common inherited disorder of lipid metabolism affecting the skeletal muscle of adults. It is an autosomal recessive disorder associated with a mutation in the enzyme carnitine palmitoyltransferase II. Carnitine palmitoyltransferase II (CPT2) is a peripheral inner mitochondrial membrane protein found in all tissues that oxidize fatty acids. It catalyzes the transesterification of palmitoylcarnitine back into palmitoyl-CoA which is a substrate for beta-oxidation inside the mitochondrial matrix. CPT2 is responsible for the formation of acylcarnitines by catalyzing the transfer of the acyl group of a long-chain fatty acyl-CoA from CoA to carnitine. Carnitine, a natural substance acquired mostly through the diet, is used by cells to process fats and produce energy. Deficiencies or mutations in the CPT2 gene lead to disorders of long-chain fatty acid oxidation. There are three forms of CPT II deficiency: (1) lethal neonatal form, (2) severe infantile hepatocardiomuscular form, and (3) the myopathic form. More than 300 CPT II deficiency cases have been described with the myopathic form being the most common (myopathic form: 86%, severe infantile form: 8%, neonatal form: 6% of cases). The myopathic form is usually mild and can manifest from infancy to adulthood. The infantile and neonatal forms are severe multisystemic diseases characterized by liver failure with hypoketotic hypoglycemia, cardiomyopathy, seizures, and early death. The adult-onset myopathic form is characterized by exercise-induced muscle pain and weakness, sometimes associated with myoglobinuria. The most common cause of hereditary myoglobinuria is the myopathic form of CPT II deficiency and affects men more than women.

Carnitine palmitoyltransferase II deficiency, which is also known as CPT II deficiency, is an inherited inborn error of metabolism (IEM) of fatty acid oxidation leading to muscle weakness. It is the most common inherited disorder of lipid metabolism affecting the skeletal muscle of adults. It is an autosomal recessive disorder associated with a mutation in the enzyme carnitine palmitoyltransferase II. Carnitine palmitoyltransferase II (CPT2) is a peripheral inner mitochondrial membrane protein found in all tissues that oxidize fatty acids. It catalyzes the transesterification of palmitoylcarnitine back into palmitoyl-CoA which is a substrate for beta-oxidation inside the mitochondrial matrix. CPT2 is responsible for the formation of acylcarnitines by catalyzing the transfer of the acyl group of a long-chain fatty acyl-CoA from CoA to carnitine. Carnitine, a natural substance acquired mostly through the diet, is used by cells to process fats and produce energy. Deficiencies or mutations in the CPT2 gene lead to disorders of long-chain fatty acid oxidation. There are three forms of CPT II deficiency: (1) lethal neonatal form, (2) severe infantile hepatocardiomuscular form, and (3) the myopathic form. More than 300 CPT II deficiency cases have been described with the myopathic form being the most common (myopathic form: 86%, severe infantile form: 8%, neonatal form: 6% of cases). The myopathic form is usually mild and can manifest from infancy to adulthood. The infantile and neonatal forms are severe multisystemic diseases characterized by liver failure with hypoketotic hypoglycemia, cardiomyopathy, seizures, and early death. The adult-onset myopathic form is characterized by exercise-induced muscle pain and weakness, sometimes associated with myoglobinuria. The most common cause of hereditary myoglobinuria is the myopathic form of CPT II deficiency and affects men more than women.

Carnitine palmitoyltransferase II deficiency, which is also known as CPT II deficiency, is an inherited inborn error of metabolism (IEM) of fatty acid oxidation leading to muscle weakness. It is the most common inherited disorder of lipid metabolism affecting the skeletal muscle of adults. It is an autosomal recessive disorder associated with a mutation in the enzyme carnitine palmitoyltransferase II. Carnitine palmitoyltransferase II (CPT2) is a peripheral inner mitochondrial membrane protein found in all tissues that oxidize fatty acids. It catalyzes the transesterification of palmitoylcarnitine back into palmitoyl-CoA which is a substrate for beta-oxidation inside the mitochondrial matrix. CPT2 is responsible for the formation of acylcarnitines by catalyzing the transfer of the acyl group of a long-chain fatty acyl-CoA from CoA to carnitine. Carnitine, a natural substance acquired mostly through the diet, is used by cells to process fats and produce energy. Deficiencies or mutations in the CPT2 gene lead to disorders of long-chain fatty acid oxidation. There are three forms of CPT II deficiency: (1) lethal neonatal form, (2) severe infantile hepatocardiomuscular form, and (3) the myopathic form. More than 300 CPT II deficiency cases have been described with the myopathic form being the most common (myopathic form: 86%, severe infantile form: 8%, neonatal form: 6% of cases). The myopathic form is usually mild and can manifest from infancy to adulthood. The infantile and neonatal forms are severe multisystemic diseases characterized by liver failure with hypoketotic hypoglycemia, cardiomyopathy, seizures, and early death. The adult-onset myopathic form is characterized by exercise-induced muscle pain and weakness, sometimes associated with myoglobinuria. The most common cause of hereditary myoglobinuria is the myopathic form of CPT II deficiency and affects men more than women.

Carnitine palmitoyltransferase II deficiency, which is also known as CPT II deficiency, is an inherited inborn error of metabolism (IEM) of fatty acid oxidation leading to muscle weakness. It is the most common inherited disorder of lipid metabolism affecting the skeletal muscle of adults. It is an autosomal recessive disorder associated with a mutation in the enzyme carnitine palmitoyltransferase II. Carnitine palmitoyltransferase II (CPT2) is a peripheral inner mitochondrial membrane protein found in all tissues that oxidize fatty acids. It catalyzes the transesterification of palmitoylcarnitine back into palmitoyl-CoA which is a substrate for beta-oxidation inside the mitochondrial matrix. CPT2 is responsible for the formation of acylcarnitines by catalyzing the transfer of the acyl group of a long-chain fatty acyl-CoA from CoA to carnitine. Carnitine, a natural substance acquired mostly through the diet, is used by cells to process fats and produce energy. Deficiencies or mutations in the CPT2 gene lead to disorders of long-chain fatty acid oxidation. There are three forms of CPT II deficiency: (1) lethal neonatal form, (2) severe infantile hepatocardiomuscular form, and (3) the myopathic form. More than 300 CPT II deficiency cases have been described with the myopathic form being the most common (myopathic form: 86%, severe infantile form: 8%, neonatal form: 6% of cases). The myopathic form is usually mild and can manifest from infancy to adulthood. The infantile and neonatal forms are severe multisystemic diseases characterized by liver failure with hypoketotic hypoglycemia, cardiomyopathy, seizures, and early death. The adult-onset myopathic form is characterized by exercise-induced muscle pain and weakness, sometimes associated with myoglobinuria. The most common cause of hereditary myoglobinuria is the myopathic form of CPT II deficiency and affects men more than women.

Carnitine is an ammonium compound that exists in two stereoisomers, of which only L-carnitine is biologically active. Carnitine can be obtained from dietary sources and also biosynthesized. It is necessary for fatty acid oxidation, transporting fatty acids from the cystosol to the mitochondria, where they are broken down via the citric acid cycle to release energy. Carnitine is synthesized from lysine residues in existing proteins. These residues are methylated using lysine methyltransferase enzymes and methyl groups from S-adenosylmethionine, then removed from the protein via hydrolysis. In the next step, the N6,N6,N6-trimethyl-L-lysine is converted to 3-hydroxy-N6,N6,N6-trimethyl-L-lysine t via the mitochondrial enzyme trimethyllysine dioxygenase. The 3-hydroxy-N6,N6,N6-trimethyl-L-lysine is then cleaved to 4-trimethylammoniobutanal and glycine, likely by an aldose identical to serine hydroxymethyltransferase. Next, 4-trimethylammoniobutanal is oxidized by the 4-trimethylaminobutyraldehyde dehydrogenase protein to 4-trimethylammoniobutanoic acid. Finally, 4-trimethylammoniobutanoic acid is transformed into L-carnitine via the enzyme gamma-butyrobetaine dioxygenase. The reactions in the carnitine synthesis pathway occur ubiquitously in the human body with the exception of the last step, as the gamma-butyrobetaine dioxygenase enzyme is found only in the liver and kidney (and at very low levels in the brain). The produced carnitine is then carried to other tissue via a number of transport systems.

Carnitine is an ammonium compound that exists in two stereoisomers, of which only L-carnitine is biologically active. Carnitine can be obtained from dietary sources and also biosynthesized. It is necessary for fatty acid oxidation, transporting fatty acids from the cystosol to the mitochondria, where they are broken down via the citric acid cycle to release energy. Carnitine is synthesized from lysine residues in existing proteins. These residues are methylated using lysine methyltransferase enzymes and methyl groups from S-adenosylmethionine, then removed from the protein via hydrolysis. In the next step, the N6,N6,N6-trimethyl-L-lysine is converted to 3-hydroxy-N6,N6,N6-trimethyl-L-lysine t via the mitochondrial enzyme trimethyllysine dioxygenase. The 3-hydroxy-N6,N6,N6-trimethyl-L-lysine is then cleaved to 4-trimethylammoniobutanal and glycine, likely by an aldose identical to serine hydroxymethyltransferase. Next, 4-trimethylammoniobutanal is oxidized by the 4-trimethylaminobutyraldehyde dehydrogenase protein to 4-trimethylammoniobutanoic acid. Finally, 4-trimethylammoniobutanoic acid is transformed into L-carnitine via the enzyme gamma-butyrobetaine dioxygenase. The reactions in the carnitine synthesis pathway occur ubiquitously in the human body with the exception of the last step, as the gamma-butyrobetaine dioxygenase enzyme is found only in the liver and kidney (and at very low levels in the brain). The produced carnitine is then carried to other tissue via a number of transport systems.

Carnitine is an ammonium compound that exists in two stereoisomers, of which only L-carnitine is biologically active. Carnitine can be obtained from dietary sources and also biosynthesized. It is necessary for fatty acid oxidation, transporting fatty acids from the cystosol to the mitochondria, where they are broken down via the citric acid cycle to release energy. Carnitine is synthesized from lysine residues in existing proteins. These residues are methylated using lysine methyltransferase enzymes and methyl groups from S-adenosylmethionine, then removed from the protein via hydrolysis. In the next step, the N6,N6,N6-trimethyl-L-lysine is converted to 3-hydroxy-N6,N6,N6-trimethyl-L-lysine t via the mitochondrial enzyme trimethyllysine dioxygenase. The 3-hydroxy-N6,N6,N6-trimethyl-L-lysine is then cleaved to 4-trimethylammoniobutanal and glycine, likely by an aldose identical to serine hydroxymethyltransferase. Next, 4-trimethylammoniobutanal is oxidized by the 4-trimethylaminobutyraldehyde dehydrogenase protein to 4-trimethylammoniobutanoic acid. Finally, 4-trimethylammoniobutanoic acid is transformed into L-carnitine via the enzyme gamma-butyrobetaine dioxygenase. The reactions in the carnitine synthesis pathway occur ubiquitously in the human body with the exception of the last step, as the gamma-butyrobetaine dioxygenase enzyme is found only in the liver and kidney (and at very low levels in the brain). The produced carnitine is then carried to other tissue via a number of transport systems.