Pathways

Tranexamic acid is a synthetic derivative of lysine used as an antifibrinolytic in the treatment and prevention of major bleeding. It targets plasminogen in blood vessels where these clots occur. The clotting process consists of two pathways, intrinsic and extrinsic, which converge to create stable fibrin which traps platelets and forms a hemostatic plug. The intrinsic pathway is activated by trauma inside the vasculature system, when there is exposed endothelial collagen. Endothelial collagen only becomes exposed when there is damage. The pathway starts with plasma kallikrein activating factor XII. The activated factor XIIa activates factor XI. Factor IX is then activated by factor XIa. Thrombin activates factor VIII and a Calicum-phospholipid-XIIa-VIIIa complex forms. This complex then activates factor X, the merging point of the two pathways. The extrinsic pathway is activated when external trauma causes blood to escape the vasculature system. Activation occurs through tissue factor released by endothelial cells after external damage. The tissue factor is a cellular receptor for factor VII. In the presence of calcium, the active site transitions and a TF-VIIa complex is formed. This complex aids in activation of factors IX and X. Factor V is activated by thrombin in the presence of calcium, then the activated factor Xa, in the presence of phospholipid, calcium and factor Va can convert prothrombin to thrombin. The extrinsic pathway occurs first, producing a small amount of thrombin, which then acts as a positive feedback on several components to increase the thrombin production. Thrombin converts fibrinogen to a loose, unstable fibrin and also activates factor XIII. Factors XIIIa strengthens the fibrin-fibrin and forms a stable, mesh fibrin which is essential for clot formation. The blood clot can be broken down by the enzyme plasmin. Plasmin is formed from plasminogen by tissue plasminogen activator. Tranexamic acid competitively and reversibly inhibits the activation of plasminogen via binding at several distinct sites, including four or five low-affinity sites and one high-affinity site. Plasmin is unable to be formed form plasminogen, and therefore, dissolution of the fibrin clot is prevented. Adverse effects such as seizures, headaches, backache, abdominal pain, nausea, vomiting, diarrhea, fatigue, pulmonary embolism, deep vein thrombosis, anaphylaxis, impaired color vision, and other visual disturbances can occur from the use of Tranexamic acid.

Trans-cinnamate, also known as trans-cinnamic acid, is an organic compound derived from cinnamic acid. Trans-cinnamate can enter the environment through industrial processes such as the manufacture of fragrances, flavorings, and pharmaceuticals. It is also a byproduct of the degradation of certain herbicides and pesticides. Bacteria such as Klebsiella electrica are capable of degrading this compound, thus detoxifying trans-cinnamate while also gaining essential carbon and energy sources for growth and metabolism. Trans-cinnamate degradation involves a sequence of enzymatic reactions converting trans-cinnamate to acetyl-CoA, a central metabolic intermediate. The compound enters the bacterial cell via facilitated diffusion upon which its degradation begins with hydroxylation by trans-cinnamate dioxygenase, followed by dehydrogenation and ring cleavage by specific dehydrogenases and dioxygenases. The intermediates are further processed to fumaric acid, pyruvic acid, and finally acetyl-CoA which enter glycolysis and citrate cycle, respectively.

Transaldolase deficiency, also known as Eyaid syndrome or TALDO deficiency, is a desease caused by homozygous or compound heterozygous mutations in the TALDO1 gene that encodes for transaldolase. The mutation found in one study was a base pair deletion leading to a premature truncation of the protein, preventing its activity in the cell. Other mutations reported in other studies include other deletions or homozygous base pair substitutions that cause a misfolded and non-functional protein. Transaldolase is an enzyme that reversibly converts D-erythrose 4-phosphate and fructose 6-phosphate to D-sedoheptulose 7-phosphate and D-glyceraldehyde 3-phosphate, as a part of the pentose phosphate pathway. Almost all affected patients show hepatosplenomegaly, liver dysfunction, low counts for all blood cell types, cardiac defects, and come from consanguinous families. They also show dysmorphic features, including a triangular face, low set ears, and a wide mouth with thin lips. Other signs include abnormal concentrations of polyols in urine and plasma, as well as ribose-, xylulose-, and ribulose-5-phosphate being elevated in urine.

Transaldolase deficiency, also known as Eyaid syndrome or TALDO deficiency, is a desease caused by homozygous or compound heterozygous mutations in the TALDO1 gene that encodes for transaldolase. The mutation found in one study was a base pair deletion leading to a premature truncation of the protein, preventing its activity in the cell. Other mutations reported in other studies include other deletions or homozygous base pair substitutions that cause a misfolded and non-functional protein. Transaldolase is an enzyme that reversibly converts D-erythrose 4-phosphate and fructose 6-phosphate to D-sedoheptulose 7-phosphate and D-glyceraldehyde 3-phosphate, as a part of the pentose phosphate pathway. Almost all affected patients show hepatosplenomegaly, liver dysfunction, low counts for all blood cell types, cardiac defects, and come from consanguinous families. They also show dysmorphic features, including a triangular face, low set ears, and a wide mouth with thin lips. Other signs include abnormal concentrations of polyols in urine and plasma, as well as ribose-, xylulose-, and ribulose-5-phosphate being elevated in urine.

Transaldolase deficiency, also known as Eyaid syndrome or TALDO deficiency, is a desease caused by homozygous or compound heterozygous mutations in the TALDO1 gene that encodes for transaldolase. The mutation found in one study was a base pair deletion leading to a premature truncation of the protein, preventing its activity in the cell. Other mutations reported in other studies include other deletions or homozygous base pair substitutions that cause a misfolded and non-functional protein. Transaldolase is an enzyme that reversibly converts D-erythrose 4-phosphate and fructose 6-phosphate to D-sedoheptulose 7-phosphate and D-glyceraldehyde 3-phosphate, as a part of the pentose phosphate pathway. Almost all affected patients show hepatosplenomegaly, liver dysfunction, low counts for all blood cell types, cardiac defects, and come from consanguinous families. They also show dysmorphic features, including a triangular face, low set ears, and a wide mouth with thin lips. Other signs include abnormal concentrations of polyols in urine and plasma, as well as ribose-, xylulose-, and ribulose-5-phosphate being elevated in urine.

Transaldolase deficiency, also known as Eyaid syndrome or TALDO deficiency, is a desease caused by homozygous or compound heterozygous mutations in the TALDO1 gene that encodes for transaldolase. The mutation found in one study was a base pair deletion leading to a premature truncation of the protein, preventing its activity in the cell. Other mutations reported in other studies include other deletions or homozygous base pair substitutions that cause a misfolded and non-functional protein. Transaldolase is an enzyme that reversibly converts D-erythrose 4-phosphate and fructose 6-phosphate to D-sedoheptulose 7-phosphate and D-glyceraldehyde 3-phosphate, as a part of the pentose phosphate pathway. Almost all affected patients show hepatosplenomegaly, liver dysfunction, low counts for all blood cell types, cardiac defects, and come from consanguinous families. They also show dysmorphic features, including a triangular face, low set ears, and a wide mouth with thin lips. Other signs include abnormal concentrations of polyols in urine and plasma, as well as ribose-, xylulose-, and ribulose-5-phosphate being elevated in urine.

Transcription is the mechanism by which a template strand of DNA is utilized by specific RNA polymerases to generate one of the three different classifications of RNA. These 3 RNA classes include messenger RNAs (mRNAs), transfer RNAs (tRNAs) and ribosomal RNAs (rRNAs). mRNAs are the genetic coding templates used by the translational machinery to determine the order of amino acids incorporated into an elongating polypeptide in the process of translation. tRNAs form covalent attachments to individual amino acids and recognize the encoded sequences of the mRNAs to allow correct insertion of amino acids into the elongating polypeptide chain. rRNAs are assembled, together with numerous ribosomal proteins, to form the ribosomes. All RNA polymerases are dependent upon a DNA template in order to synthesize RNA. The resultant RNA is, therefore, complimentary to the template strand of the DNA duplex and identical to the non-template strand. In eukaryotic cells there are 3 distinct classes of RNA polymerase, RNA polymerase (pol) I, II and III. Each polymerase is responsible for the synthesis of a different class of RNA. Once the mRNA transcript is generated, it is available for translation through the action of the ribosome and activated amino-acid tRNA carriers. For protein synthesis, a succession of tRNA molecules charged with appropriate amino acids have to be brought together with an mRNA molecule and matched up by base-pairing through their anti-codons with each of its successive codons. The amino acids then have to be linked together to extend the growing protein chain, and the tRNAs, relieved of their burdens, have to be released. This whole complex of processes is carried out by a giant multimolecular machine, the ribosome, formed of two main chains of RNA, called ribosomal RNA (rRNA), and more than 50 different proteins. The synthesis of proteins is known as translation. Translation occurs in the cytoplasm where the ribosomes are located. Ribosomes are made of a small and large subunit which surrounds the mRNA. In translation, messenger RNA (mRNA) is decoded to produce a specific polypeptide according to the rules specified by the trinucleotide genetic code. This uses an mRNA sequence as a template to guide the synthesis of a chain of amino acids that form a protein. Translation proceeds in four phases: activation, initiation, elongation and termination (all describing the growth of the amino acid chain, or polypeptide that is the product of translation). In activation, the correct amino acid is joined to the correct transfer RNA (tRNA). While this is not technically a step in translation, it is required for translation to proceed. The amino acid is joined by its carboxyl group to the 3’ OH of the tRNA by an ester bond. When the tRNA has an amino acid linked to it, it is termed “charged”. Initiation involves the small subunit of the ribosome binding to 5’ end of mRNA with the help of initiation factors (IF), other proteins that assist the process. Elongation occurs when the next aminoacyl-tRNA (charged tRNA) in line binds to the ribosome along with GTP and an elongation factor. Termination of the polypeptide happens when the A site of the ribosome faces a stop codon (UAA, UAG, or UGA). When this happens, no tRNA can recognize it, but releasing factor can recognize nonsense codons and causes the release of the polypeptide chain.

Acetyl-CoA is an important molecule, which is precursor to HMG CoA, which is a vital component in cholesterol and ketone synthesis. Acetyl CoA participates in the biosynthesis of fatty acids and sterols, in the oxidation of fatty acids and in the metabolism of many amino acids. It also acts as a biological acetylating agent. Acetyl-CoA is made in the mitochondria by metabolizing fatty acids, and the oxidation of pyruvate of acetyl-CoA. When the body has an excess of ATP, the energy in acetyl-Coa can be stored in the form of fatty acids. Acetyl-CoA must cross the mitochondrial membrane to the cytosol, where fatty acid synthesis takes place. Acetyl-CoA is combined with oxalacetic acid by the enzyme citrate synthase, creating citric acid. Citric acid is then transported out of the mitochondria, to the cytosol, where the enzyme citrate lyase converts citric acid back into acetyl-CoA and oxalacetic acid. Malate dehydrogenase reduces oxalacetic acid to malate, which then is either transported back into the mitochondria by the malate-alpha ketoglutarate transporter or oxidized to pyruvate by malic enzyme. Pyruvate can then be transported back into the mitochondria and undergo decarboxylation into oxalacetic acid. Malate can also be used to create NADH by the conversion of malate to oxalacetic acid by malate dehydrogenase.

Acetyl-CoA is an important molecule, which is precursor to HMG CoA, which is a vital component in cholesterol and ketone synthesis. Acetyl CoA participates in the biosynthesis of fatty acids and sterols, in the oxidation of fatty acids and in the metabolism of many amino acids. It also acts as a biological acetylating agent. Acetyl-CoA is made in the mitochondria by metabolizing fatty acids, and the oxidation of pyruvate of acetyl-CoA. When the body has an excess of ATP, the energy in acetyl-Coa can be stored in the form of fatty acids. Acetyl-CoA must cross the mitochondrial membrane to the cytosol, where fatty acid synthesis takes place. Acetyl-CoA is combined with oxalacetic acid by the enzyme citrate synthase, creating citric acid. Citric acid is then transported out of the mitochondria, to the cytosol, where the enzyme citrate lyase converts citric acid back into acetyl-CoA and oxalacetic acid. Malate dehydrogenase reduces oxalacetic acid to malate, which then is either transported back into the mitochondria by the malate-alpha ketoglutarate transporter or oxidized to pyruvate by malic enzyme. Pyruvate can then be transported back into the mitochondria and undergo decarboxylation into oxalacetic acid. Malate can also be used to create NADH by the conversion of malate to oxalacetic acid by malate dehydrogenase.