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Showing 48681 - 48690 of 48701 pathways
SMPDB ID Pathway Chemical Compounds Proteins

SMP0000636

Pw000612 View Pathway
Drug Metabolism

Venlafaxine Metabolism Pathway

Venlafaxine (also named as Effexor or Elafax) is an antidepressant medication, which belongs to the class of serotonin-norepinephrine reuptake inhibitor (SNRI). Venlafaxine is well absorbed into the circulation system. Venlafaxine is also metabolized to N-desmethylvenlafaxine. The N-demethylation is catalyzed by CYP3A4 and CYP2C19. N-desmethylvenlafaxine is a weaker serotonin and norepinephrine reuptake inhibitor. Both O-desmethylvenlafaxine (as potent a serotonin-norepinephrine reuptake inhibitor) and N-desmethylvenlafaxine are further metabolized by CYP2C19, CYP2D6 and/or CYP3A4 to a minor metabolite N,O-didesmethylvenlafaxine that is further metabolized into N,N,O-tridesmethylvenlafaxine or excreted as N,O-didesmethylvenlafaxine gucuronide. Later on, O-desmethylvenlafaxine is exported without any change in chemical structure. Venlafaxine is exported via two transporters: Multidrug resistance protein 1 and ATP-binding cassette sub-family G member 2.

SMP0000375

Pw000390 View Pathway
Drug Action

Verapamil Action Pathway

Verapamil is a phenylalkylamine calcium channel blocker (CCB) or antagonist. There are at least five different types of calcium channels in Homo sapiens: L-, N-, P/Q-, R- and T-type. CCBs target L-type calcium channels, the major channel in muscle cells that mediates contraction. Verapamil, an organic cation, is thought to primarily block L-type calcium channels in their open state by interfering with the binding of calcium ions to the extracellular opening of the channel. It is one of only two clinically used CCBs that are cardioselective. Verapamil and diltiazem and, the other cardioselective CCB, shows greater activity against cardiac calcium channels than those of the peripheral vasculature. Other CCBs, such as nifedipine and amlodipine, have little to no effect on cardiac cells (cardiac myocytes and cells of the SA and AV nodes). Due to its cardioselective properties, verapamil may be used to treat arrhythmias (e.g. atrial fibrillation) as well as hypertension. The first part of this pathway depicts the pharmacological action of verapamil on cardiac myocytes and peripheral arterioles and coronary arteries. Verapamil decreases cardiac myocyte contractility by inhibiting the influx of calcium ions. Calcium ions entering the cell through L-type calcium channels bind to calmodulin. Calcium-bound calmodulin then binds to and activates myosin light chain kinase (MLCK). Activated MLCK catalyzes the phosphorylation of the regulatory light chain subunit of myosin, a key step in muscle contraction. Signal amplification is achieved by calcium-induced calcium release from the sarcoplasmic reticulum through ryanodine receptors. Inhibition of the initial influx of calcium decreases the contractile activity of cardiac myocytes and results in an overall decreased force of contraction by the heart. Verapamil affects smooth muscle contraction and subsequent vasoconstriction in peripheral arterioles and coronary arteries by the same mechanism. Decreased cardiac contractility and vasodilation lower blood pressure. The second part of this pathway illustrates the effect of calcium channel antagonism on the cardiac action potentials. Contractile activity of cardiac myocytes is elicited via action potentials mediated by a number of ion channel proteins. During rest, or diastole, cells maintain a negative membrane potential; i.e. the inside of the cell is negatively charged relative to the cellsŠ—È extracellular environment. Membrane ion pumps, such as the sodium-potassium ATPase and sodium-calcium exchanger (NCX), maintain low intracellular sodium (5 mM) and calcium (100 nM) concentrations and high intracellular potassium (140 mM) concentrations. Conversely, extracellular concentrations of sodium (140 mM) and calcium (1.8 mM) are relatively high and extracellular potassium concentrations are low (5 mM). At rest, the cardiac cell membrane is impermeable to sodium and calcium ions, but is permeable to potassium ions via inward rectifier potassium channels (I-K1), which allow an outward flow of potassium ions down their concentration gradient. The positive outflow of potassium ions aids in maintaining the negative intracellular electric potential. When cells reach a critical threshold potential, voltage-gated sodium channels (I-Na) open and the rapid influx of positive sodium ions into the cell occurs as the ions travel down their electrochemical gradient. This is known as the rapid depolarization or upstroke phase of the cardiac action potential. Sodium channels then close and rapidly activated potassium channels such as the voltage-gated transient outward delayed rectifying potassium channel (I-Kto) and the voltage-gated ultra rapid delayed rectifying potassium channel (I-Kur) open. These events make up the early repolarization phase during which potassium ions flow out of the cell and sodium ions are continually pumped out. During the next phase, known as the plateau phase, calcium L-type channels (I-CaL) open and the resulting influx of calcium ions roughly balances the outward flow of potassium channels. During the final repolarization phase, the voltage-gated rapid (I-Kr) and slow (I-Ks) delayed rectifying potassium channels open increasing the outflow of potassium ions and repolarizing the cell. The extra sodium and calcium ions that entered the cell during the action potential are extruded via sodium-potassium ATPases and NCX and intra- and extracellular ion concentrations are restored. In specialized pacemaker cells, gradual depolarization to threshold occurs via funny channels (I-f). Blocking L-type calcium channels decreases conduction and increases the refractory period. VerapamilŠ—Ès effects on pacemaker cells enable its use as a rate-controlling agent in atrial fibrillation.

SMP0000540

Pw000516 View Pathway
Disease

Very-Long-Chain Acyl-CoA Dehydrogenase Deficiency (VLCAD)

Very long-chain acyl-CoA dehydrogenase deficiency (VLCAD), also called ACADL and VLCAD, is a rare inborn error of metabolism (IEM) and autosomal recessive disorder, which is caused by a defective very long-chain specific acyl-CoA dehydrogenase. Very long-chain specific acyl-CoA dehydrogenase breakdown certain fats to energy. This disorder is characterized by a large accumulation of fatty acids such as L-Palmitoylcarnitine in the mitochondria. Symptoms of the disorder include muscle weakness, lethargy (lack of energy) and hypoglycemia (low blood sugar). Treatment with diet modifications such as consuming supplemental calories is suggested. It is estimated that very long-chain acyl-CoA dehydrogenase deficiency affects 1 in 40,000 to 120,000 individuals.

SMP0000436

Pw000241 View Pathway
Drug Action

Vinblastine Action Pathway

Vinblastine (also named Velban) is a natural alkaloid isolated from the leaves of the Catharanthus roseus (commonly known as the Madagascar periwinkle). Vinblastine are used as chemotherapy medication such as an antimitotic anticancer agent. The mechanism of vinblastine is the inhibition of microtubule dynamics that would cause mitotic arrest and eventual cell death. As a microtubule destabilizing agent, Vinblastine stimulates mitotic spindle destruction and microtubule depolymerization at high concentrations. At lower clinically relevant concentrations, vinblastine can block mitotic progression. Unlike the taxanes, which bind poorly to soluble tubulin, vinblastine can bind both soluble and microtubule-associated tubulin. To be able stabilizing the kinetics of microtule, vinblastine rapidly and reversibly bind to soluble tubulin which can increase the affinity of tublin by the induction of conformational changes of tubulin. Vinblastine binds to β-tubulin subunits at the positive end of microtubules at a region called the _Vinca_-binding domain. Binding between vinblastine and solubale tubulin decreases the rate of microtubule dynamics (lengthening and shortening) and increases the duration of attenuated state of microtubules. Therefore, the proper assembly of the mitotic spindle could be prevented; and the tension at the kinetochores of the chromosomes could be reduced. Subsequently, chromosomes can not progress to the spindle equator at the spindle poles. Progression from metaphase to anaphase is blocked and cells enter a state of mitotic arrest. The cells may then undergo one of several fates. The tetraploid cell may undergo unequal cell division producing aneuploid daughter cells. Alternatively, it may exit the cell cycle without undergoing cell division, a process termed mitotic slippage or adaptation. These cells may continue progressing through the cell cycle as tetraploid cells (Adaptation I), may exit G1 phase and undergo apoptosis or senescence (Adaption II), or may escape to G1 and undergo apoptosis during interphase (Adaptation III). Another possibility is cell death during mitotic arrest. Alternatively, mitotic catastrophe may occur and cause cell death. Vinca alkaloids are also thought to increase apoptosis by increasing concentrations of p53 (cellular tumor antigen p53) and p21 (cyclin-dependent kinase inhibitor 1) and by inhibiting Bcl-2 activity. Increasing concentrations of p53 and p21 lead to changes in protein kinase activity. Phosphorylation of Bcl-2 subsequently inhibits the formation Bcl-2-BAX heterodimers. This results in decreased anti-apoptotic activity. One way in which cells have developed resistance against the vinca alkaloids is by drug efflux. Drug efflux is mediated by a number of multidrug resistant transporters as depicted in this pathway.

SMP0000437

Pw000242 View Pathway
Drug Action

Vincristine Action Pathway

Vincristine (also named leurocristine) is a natural alkaloid isolated from the leaves of the Catharanthus roseus (commonly known as the Madagascar periwinkle). Vincristine are used as chemotherapy medication such as an antimitotic anticancer agent. The mechanism of vincristine is the inhibition of microtubule dynamics that would cause mitotic arrest and eventual cell death. As a microtubule destabilizing agent, Vincristine stimulates mitotic spindle destruction and microtubule depolymerization at high concentrations. At lower clinically relevant concentrations, vincristine can block mitotic progression. Unlike the taxanes, which bind poorly to soluble tubulin, vincristine can bind both soluble and microtubule-associated tubulin. To be able stabilizing the kinetics of microtule, vincristine rapidly and reversibly bind to soluble tubulin which can increase the affinity of tublin by the induction of conformational changes of tubulin. Vincristine binds to β-tubulin subunits at the positive end of microtubules at a region called the _Vinca_-binding domain. Binding between vincristine and solubale tubulin decreases the rate of microtubule dynamics (lengthening and shortening) and increases the duration of attenuated state of microtubules. Therefore, the proper assembly of the mitotic spindle could be prevented; and the tension at the kinetochores of the chromosomes could be reduced. Subsequently, chromosomes can not progress to the spindle equator at the spindle poles. Progression from metaphase to anaphase is blocked and cells enter a state of mitotic arrest. The cells may then undergo one of several fates. The tetraploid cell may undergo unequal cell division producing aneuploid daughter cells. Alternatively, it may exit the cell cycle without undergoing cell division, a process termed mitotic slippage or adaptation. These cells may continue progressing through the cell cycle as tetraploid cells (Adaptation I), may exit G1 phase and undergo apoptosis or senescence (Adaption II), or may escape to G1 and undergo apoptosis during interphase (Adaptation III). Another possibility is cell death during mitotic arrest. Alternatively, mitotic catastrophe may occur and cause cell death. Vinca alkaloids are also thought to increase apoptosis by increasing concentrations of p53 (cellular tumor antigen p53) and p21 (cyclin-dependent kinase inhibitor 1) and by inhibiting Bcl-2 activity. Increasing concentrations of p53 and p21 lead to changes in protein kinase activity. Phosphorylation of Bcl-2 subsequently inhibits the formation Bcl-2-BAX heterodimers. This results in decreased anti-apoptotic activity. One way in which cells have developed resistance against the vinca alkaloids is by drug efflux. Drug efflux is mediated by a number of multidrug resistant transporters as depicted in this pathway.

SMP0000438

Pw000243 View Pathway
Drug Action

Vindesine Action Pathway

Vindesine (also named Eldesine) is a semisynthetic vinca alkaloid. Vindesine are used as chemotherapy medication such as an antimitotic anticancer agent. The mechanism of vindesine is the inhibition of microtubule dynamics that would cause mitotic arrest and eventual cell death. As a microtubule destabilizing agent, vindesine stimulates mitotic spindle destruction and microtubule depolymerization at high concentrations. At lower clinically relevant concentrations, vindesine can block mitotic progression. Unlike the taxanes, which bind poorly to soluble tubulin, vindesine can bind both soluble and microtubule-associated tubulin. To be able stabilizing the kinetics of microtule, vindesine rapidly and reversibly bind to soluble tubulin which can increase the affinity of tublin by the induction of conformational changes of tubulin. Vindesine binds to β-tubulin subunits at the positive end of microtubules at a region called the _Vinca_-binding domain. Binding between vindesine and solubale tubulin decreases the rate of microtubule dynamics (lengthening and shortening) and increases the duration of attenuated state of microtubules. Therefore, the proper assembly of the mitotic spindle could be prevented; and the tension at the kinetochores of the chromosomes could be reduced. Subsequently, chromosomes can not progress to the spindle equator at the spindle poles. Progression from metaphase to anaphase is blocked and cells enter a state of mitotic arrest. The cells may then undergo one of several fates. The tetraploid cell may undergo unequal cell division producing aneuploid daughter cells. Alternatively, it may exit the cell cycle without undergoing cell division, a process termed mitotic slippage or adaptation. These cells may continue progressing through the cell cycle as tetraploid cells (Adaptation I), may exit G1 phase and undergo apoptosis or senescence (Adaption II), or may escape to G1 and undergo apoptosis during interphase (Adaptation III). Another possibility is cell death during mitotic arrest. Alternatively, mitotic catastrophe may occur and cause cell death. Vinca alkaloids are also thought to increase apoptosis by increasing concentrations of p53 (cellular tumor antigen p53) and p21 (cyclin-dependent kinase inhibitor 1) and by inhibiting Bcl-2 activity. Increasing concentrations of p53 and p21 lead to changes in protein kinase activity. Phosphorylation of Bcl-2 subsequently inhibits the formation Bcl-2-BAX heterodimers. This results in decreased anti-apoptotic activity. One way in which cells have developed resistance against the vinca alkaloids is by drug efflux. Drug efflux is mediated by a number of multidrug resistant transporters as depicted in this pathway.

SMP0000439

Pw000244 View Pathway
Drug Action

Vinorelbine Action Pathway

Vinorelbine (also named Navelbine) is a semisynthetic vinca alkaloid. Vinorelbine are used as chemotherapy medication such as an antimitotic anticancer agent. The mechanism of vinorelbine is the inhibition of microtubule dynamics that would cause mitotic arrest and eventual cell death. As a microtubule destabilizing agent, vinorelbine stimulates mitotic spindle destruction and microtubule depolymerization at high concentrations. At lower clinically relevant concentrations, vinorelbine can block mitotic progression. Unlike the taxanes, which bind poorly to soluble tubulin, vinorelbine can bind both soluble and microtubule-associated tubulin. To be able stabilizing the kinetics of microtule, vinorelbine rapidly and reversibly bind to soluble tubulin which can increase the affinity of tublin by the induction of conformational changes of tubulin. Vinorelbine binds to β-tubulin subunits at the positive end of microtubules at a region called the _Vinca_-binding domain. Binding between vinorelbine and solubale tubulin decreases the rate of microtubule dynamics (lengthening and shortening) and increases the duration of attenuated state of microtubules. Therefore, the proper assembly of the mitotic spindle could be prevented; and the tension at the kinetochores of the chromosomes could be reduced. Subsequently, chromosomes can not progress to the spindle equator at the spindle poles. Progression from metaphase to anaphase is blocked and cells enter a state of mitotic arrest. The cells may then undergo one of several fates. The tetraploid cell may undergo unequal cell division producing aneuploid daughter cells. Alternatively, it may exit the cell cycle without undergoing cell division, a process termed mitotic slippage or adaptation. These cells may continue progressing through the cell cycle as tetraploid cells (Adaptation I), may exit G1 phase and undergo apoptosis or senescence (Adaption II), or may escape to G1 and undergo apoptosis during interphase (Adaptation III). Another possibility is cell death during mitotic arrest. Alternatively, mitotic catastrophe may occur and cause cell death. Vinca alkaloids are also thought to increase apoptosis by increasing concentrations of p53 (cellular tumor antigen p53) and p21 (cyclin-dependent kinase inhibitor 1) and by inhibiting Bcl-2 activity. Increasing concentrations of p53 and p21 lead to changes in protein kinase activity. Phosphorylation of Bcl-2 subsequently inhibits the formation Bcl-2-BAX heterodimers. This results in decreased anti-apoptotic activity. One way in which cells have developed resistance against the vinca alkaloids is by drug efflux. Drug efflux is mediated by a number of multidrug resistant transporters as depicted in this pathway.

SMP0000336

Pw000210 View Pathway
Disease

Vitamin A Deficiency

Vitamin A deficiency can be caused by many causes. A defect in the BCMO1 gene which codes for beta,beta-carotene 15,15’-monooxygenase is one of them. Beta,beta-carotene 15,15’-monooxygenase catalyzes the chemical reaction where the two substrates are beta-carotene and O2, whereas its product is retinal. A defect in this enzyme results in decrease of levels of retinal and vitamin A in serum; Signs and symptoms include night blindness, poor adaptation to darkness, dry skin and hair.

SMP0000017

Pw000053 View Pathway
Metabolic

Vitamin B6 Metabolism

As is commonly known there are many vitamins, the vitamin B complex group being one of the most well known. An important vitamin B complex group vitamin is vitamin B6, which is water-soluble. Moreover, this vitamin comes in various forms, one of which is an active form, known by the name pyridoxal phosphate or PLP. PLP serves as cofactor in a variety of reactions including from amino acid metabolism, (in particular in reactions such as transamination, deamination, and decarboxylation). To complicate matters however, there are in fact seven alternate forms of this same vitamin. These include pyridoxine (PN), pyridoxine 5’-phosphate (PNP), pyridoxal (PL), pyridoxamine (PM), pyridoxamine 5’-phosphate (PMP), 4-pyridoxic acid (PA), and the aforementioned pyridoxal 5’-phosphate (PLP). One of these forms, PA, is in fact a catabolite whose presence is found in excreted urine. For a person to absorb some of these active forms of vitamin B6 such as PLP or PMP they must first be dephosphorylized. This done via an alkaline enzyme phosphatase. There are a wide variety of biproducts from the metabolism in question, most of which find there ways into the urine and from there are excreted. One such biproduct is 4-pyridoxic acid. In fact this last biproduct is found in such large quantities that estimates of vitamin B6 metabolism birproducts show that 4-pyridoxic acid is as much as 40-60% of all the biproducts.Of course, it is not the only product of metabolism. Others include,include pyridoxal, pyridoxamine, and pyridoxine.

SMP0000464

Pw000047 View Pathway
Metabolic

Vitamin K Metabolism

Vitamin K describes a group of lipophilic, hydrophobic vitamins that exist naturally in two forms (and synthetically in three others): vitamin K1, which is found in plants, and vitamin K2, which is synthesized by bacteria. Vitamin K is an important dietary component because it is necessary as a cofacter in the activation of vitamin K dependent proteins. Metabolism of vitamin K occurs mainly in the liver. In the first step, vitamin K is reduced to its quinone form by a quinone reductase such as NAD(P)H dehydrogenase. Reduced vitamin K is the form required to convert vitamin K dependent protein precursors to their active states. It acts as a cofactor to the integral membrane enzyme vitamin K-dependent gamma-carboxylase (along with water and carbon dioxide as co-substrates), which carboxylates glutamyl residues to gamma-carboxy-glutamic acid residues on certain proteins, activating them. Each converted glutamyl residue produces a molecule of vitamin K epoxide, and certain proteins may have more than one residue requiring carboxylation. To complete the cycle, the vitamin K epoxide is returned to vitamin K via the vitamin K epoxide reductase enzyme, also an integral membrane protein. The vitamin K dependent proteins include a number of important coagulation factors, such as prothrombin. Thus, warfarin and other coumarin drugs act as anticoagulants by blocking vitamin K epoxide reductase.
Showing 48681 - 48690 of 48701 pathways