20 octobre 2012

Biological role of L-DOPA

L-tyrosine by the enzyme tyrosine hydroxylase (TH). It is also the precursor for the monoamine or catecholamine neurotransmitters dopamine, norepinephrine (noradrenaline), and epinephrine (adrenaline). Dopamine is formed by the decarboxylation of L-DOPA. L-DOPA can be directly metabolized by catechol-O-methyl transferase (COMT) to 3-O-methyldopa (3-OMD), and then further to vanillactic acid (VLA). This metabolic pathway is non-existent in the healthy body, but becomes important after peripheral L-DOPA administration in patients with... [Lire la suite]
Posté par tnfalpha à 15:31 - Commentaires [0] - Permalien [#]

20 octobre 2012

Therapeutic use of L-DOPA

L-DOPA crosses the protective blood–brain barrier, whereas dopamine itself cannot. Thus, L-DOPA is used to increase dopamine concentrations in the treatment of Parkinson's disease and dopamine-responsive dystonia. This treatment was originally developed by George Cotzias and his coworkers. Once L-DOPA has entered the central nervous system, it is converted into dopamine by the enzyme aromatic L-amino acid decarboxylase, also known as DOPA decarboxylase (DDC). Pyridoxal phosphate (vitamin B6) is a required cofactor in this reaction,... [Lire la suite]
Posté par tnfalpha à 15:31 - Commentaires [0] - Permalien [#]
20 octobre 2012

L-DOPA

L-DOPA (L-3,4-dihydroxyphenylalanine) is a chemical that is made and used as part of the normal biology of some animals and plants. Some animals including humans make it via biosynthesis from the amino acid L-tyrosine. L-DOPA is the precursor to the neurotransmitters dopamine, norepinephrine (noradrenaline), and epinephrine (adrenaline) collectively known as catecholamines. L-DOPA can be manufactured and in its pure form is sold as a psychoactive drug with the INN levodopa; trade names include Sinemet, Parcopa, Atamet, Stalevo,... [Lire la suite]
Posté par tnfalpha à 15:29 - Commentaires [0] - Permalien [#]
19 octobre 2012

Metal binding of Metallothionein

Metallothionein has been documented to bind a wide range of metals including cadmium, zinc, mercury, copper, arsenic, silver, etc. Metallation of MT was previously reported to occur cooperatively but recent reports have provided strong evidence that metal-binding occurs via a sequential, noncooperative mechanism. The observation of partially metallated MT (that is, having some free metal binding capacity) suggest that these species are biologically important.Metallothioneins likely participate in the uptake, transport, and regulation... [Lire la suite]
Posté par tnfalpha à 09:36 - Commentaires [0] - Permalien [#]
19 octobre 2012

Structure and classification of Metallothionein

Metallothioneins are present in a vast range of taxonomic groups, ranging from prokaryotes (such as the cyanobacteria Syneccococus spp....), protozoa (p. ex. the ciliate Tetrahymena genera...), plants (such as Pisum sativum, Triticum durum, Zea mays, Quercus suber...), yeast (such as Saccharomyces cerevisiae, Candida albicans,...), invertebrates (such as the nematode Caenorhabditis elegans, the insect Drosophila melanogaster, the mollusc Mytilus edulis, or the echinoderm Strongylocentrotus purpuratus) and vertebrates (such as the... [Lire la suite]
Posté par tnfalpha à 09:35 - Commentaires [0] - Permalien [#]
19 octobre 2012

Metallothionein

Metallothionein (MT) is a family of cysteine-rich, low molecular weight (MW ranging from 500 to 14000 Da) proteins. They are localized to the membrane of the Golgi apparatus. MTs have the capacity to bind both physiological (such as zinc, copper, selenium) and xenobiotic (such as cadmium, mercury, silver, arsenic) heavy metals through the thiol group of its cysteine residues, which represents nearly the 30% of its amino acidic residues.MT was discovered in 1957 by Vallee and Margoshe from purification of a Cd-binding protein from... [Lire la suite]
Posté par tnfalpha à 09:35 - Commentaires [0] - Permalien [#]

17 octobre 2012

Entrez Gene summary for CYP24A1

CYP24A1 encodes a member of the cytochrome P450 superfamily of enzymes. The cytochrome P450 proteins aremonooxygenases which catalyze many reactions involved in drug metabolism and synthesis of cholesterol, steroids andother lipids. This mitochondrial protein initiates the degradation of 1,25-dihydroxyvitamin D3, the physiologicallyactive form of vitamin D3, by hydroxylation of the side chain. In regulating the level of vitamin D3, this enzymeplays a role in calcium homeostasis and the vitamin D endocrine system. Alternatively spliced... [Lire la suite]
Posté par tnfalpha à 14:58 - Commentaires [0] - Permalien [#]
17 octobre 2012

Function of CYP24A1

This mitochondrial protein initiates the degradation of 1,25-dihydroxyvitamin D3, the physiologically active form of vitamin D3, by hydroxylation of the side chain to form calcitroic acid.In regulating the level of vitamin D3, this enzyme plays a role in calcium homeostasis and the vitamin D endocrine system.Has a role in maintaining calcium homeostasis. Catalyzes the NADPH-dependent 24-hydroxylation of calcidiol(25-hydroxyvitamin D(3)) and calcitriol (1-alpha,25-dihydroxyvitamin D(3)). CYP24A1 can perform up to 6 rounds... [Lire la suite]
Posté par tnfalpha à 14:57 - Commentaires [0] - Permalien [#]
17 octobre 2012

CYP24A1

De1,25-dihydroxyvitamin D3 24-hydroxylase, mitochondrial is an enzyme that in humans is encoded by the CYP24A1 gene.This gene encodes a member of the cytochrome P450 superfamily of enzymes. The cytochrome P450 proteins are monooxygenases which catalyze many reactions involved in drug metabolism and synthesis of cholesterol, steroids and other lipids.
Posté par tnfalpha à 14:57 - Commentaires [0] - Permalien [#]
14 octobre 2012

Knockout phenotype of Desmin

When the gene for desmin is knocked out it is no longer able to function properly. Mice with the desmin knockout gene develop normally and are fertile, however soon after birth they begin to show defects in skeletal, smooth and cardiac muscle; in particular the diaphragm and heart are affected. The mice without desmin are weaker and fatigue more easily than wild type mice and the muscle fibers are more likely to be damaged during contraction, presumably because the desmin is responsible for keeping the muscle fibers aligned. Mice... [Lire la suite]
Posté par tnfalpha à 11:00 - Commentaires [0] - Permalien [#]