Carnitine Acyltransferase System

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Carnitine Acyltransferase System
Carnitine Acyltransferase System
The Carnitine Acyltransferase System. A translocase (the carnitine-acylcarnitine transporter , CACT ) is required so that the fatty acid (acylcarnitine, 2 ) bound to Lcarnitine ( 1 ) can get from the intermembrane space into the mitochondrial matrix . The carnitine acyltransferase 1 (also known as carnitine palmitoyltransferase 1, CPT1 , known) which is at the outer mitochondrial membrane, Carntin acyltransferase 2 (or carnitine Palmitolytransferase 2, 2 CPT- localized) on the inner mitochondrial membrane. Malonyl-CoA inhibits CPT-1. It is a product of acetyl-CoA carboxylase and an important intermediate in fatty acid synthesis . The proportions in the illustration are not true to scale
Transporter classification
TCDB 4.C.2
designation CrAT family

The carnitine acyltransferase system is an important transport system in biology , consisting of several enzymes that are used to transport fatty acids into the mitochondria . There energy is obtained from the fatty acids as part of the β-oxidation .

Basics

Triglycerides are made up of fatty acids and glycerine and are important stores of energy. They reach the small intestine with food intake via the esophagus and stomach and are broken down into free fatty acids and glycerol by lipolysis with the help of pancreatic lipase . The two products of lipolysis can be absorbed as a complex with bile acids , so-called micelles, i.e. taken up by the epithelial cells of the small intestine. In the cells, triglycerides are formed again from the free fatty acids and glycerine, which are packed with apolipoproteins and transported to the tissues in the form of chylomicrons via the lymphatic system and the bloodstream.

The transport of fatty acids from the cytosol into the mitochondrial matrix, the site of β-oxidation, is catalyzed by various carnitine acyltransferases, acyl-CoA synthetase and carnitine / acylcarnitine translocase. According to current understanding, there are three different carnitine acyltransferases with different specificities for different chain lengths of the substrates. Specifically, these are carnitine acyl transferase (CAT), carnitine octanyl transferase (COT) and carnitine palmityl transferase (CPT). In contrast to the CPT fraction, the CAT and COT are completely soluble.

genetics

The carnitine-palmityl transferase system consists of two immunologically distinct components encoded on different genes: the carnitine-palmityl transferase 1 (CPT-1; EC  2.3.1.21 ) and the carnitine-palmityl transferase 2 (CPT-2). While CPT 2 was assigned to chromosome 1 gene locus p32 as a single protein , there are separate genes for each of the isoforms of CPT-1, so that L-CPT 1 on chromosome 11 gene locus q13 and the muscle isoform (M-CPT 1) on chromosome 22 gene locus q13.3 is encoded.

Individual evidence

  1. ↑ Thomas M. Devlin (Ed.): Textbook of Biochemistry with Clinical Correlations . Wiley & Sons; 6th edition 2005; ISBN 0-471-67808-2 ; P. 681.
  2. ↑ M. Zerbaum: Investigation of the substrate specificity of carnitine palmityl transferase 1 and 2 in human skeletal muscle for even-numbered fatty acids with 8 to 18 carbon atoms. Original work .
  3. ↑ LL. Bieber: Carnitine . In: Ann Rev Biochem 57 (1988) 261-283; PMID 3052273 ; doi : 10.1146 / annurev.bi.57.070188.001401
  4. ^ J. Bremer: Carnitine - metabolism and functions . In: Physiol Rev 63 (4) (1983) 1420-1480; PMID 6361812
  5. ↑ S. Miyazawa et al .: Purification and properties of carnitine octanoyltransferase and carnitine palmitoyltransferase from rat liver . In: J Biochem 94 (2) (1983); 529-542; PMID 6630173 .
  6. ^ CH Britton, DW Mackey a. a .: Fine chromosome mapping of the genes for human liver and muscle carnitine palmitoyltransferase I (CPT1A and CPT1B). In: Genomics. Volume 40, Number 1, February 1997, pp. 209-211, ISSN  0888-7543 . doi : 10.1006 / geno.1996.4539 . PMID 9070950 .
  7. ↑ C. Gellera, E. Verderio et al. a .: Assignment of the human carnitine palmitoyltransferase II gene (CPT1) to chromosome 1p32. In: Genomics. Volume 24, Number 1, November 1994, pp. 195-197, ISSN  0888-7543 . doi : 10.1006 / geno.1994.1605 . PMID 7896283 .