Target type: molecularfunction
Catalysis of the reaction: L-Selenocystathionine + H2O => L-Selenocysteine + NH3 + 2-Oxobutanoic acid. [PMID:6456763]
Selenocystathionine gamma-lyase activity is a crucial enzymatic function involved in the metabolism of selenocysteine, a rare amino acid essential for the synthesis of selenoproteins. Selenoproteins are proteins that contain selenocysteine in their polypeptide chain, and they play vital roles in a variety of cellular processes, including redox homeostasis, thyroid hormone metabolism, and immune function.
Selenocystathionine gamma-lyase catalyzes the breakdown of selenocystathionine, a sulfur-containing amino acid, into cysteine, ammonia, and α-ketobutyrate. This reaction is a critical step in the biosynthesis of selenocysteine. Selenocysteine is incorporated into selenoproteins during protein translation by a unique mechanism that involves a special tRNA and a dedicated elongation factor.
The enzyme selenocystathionine gamma-lyase is a member of the cystathionine β-synthase family of enzymes. These enzymes are characterized by their ability to cleave carbon-sulfur bonds. In the case of selenocystathionine gamma-lyase, the enzyme specifically cleaves the carbon-selenium bond in selenocystathionine.
The active site of selenocystathionine gamma-lyase contains a pyridoxal phosphate (PLP) cofactor, which is essential for catalytic activity. The PLP cofactor is bound to the enzyme via a Schiff base linkage to a lysine residue. During the catalytic cycle, the PLP cofactor undergoes a series of chemical transformations that facilitate the cleavage of the carbon-selenium bond in selenocystathionine.
Deficiency in selenocystathionine gamma-lyase activity can lead to a buildup of selenocystathionine in the body, which can have adverse effects on health. Selenocystathionine gamma-lyase activity is also important for the detoxification of hydrogen sulfide, a toxic gas that is produced by the body as a byproduct of metabolism.
In summary, selenocystathionine gamma-lyase activity is a key enzyme in selenocysteine biosynthesis, a process that is essential for the synthesis of selenoproteins. These proteins are involved in a variety of cellular functions, including redox homeostasis, thyroid hormone metabolism, and immune function. Selenocystathionine gamma-lyase activity also plays a role in the detoxification of hydrogen sulfide.'
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| Protein | Definition | Taxonomy |
|---|---|---|
| Cystathionine gamma-lyase | A cystathionine gamma-lyase that is encoded in the genome of human. [PRO:DNx, UniProtKB:P32929] | Homo sapiens (human) |
| Compound | Definition | Classes | Roles |
|---|---|---|---|
| aminooxyacetic acid | (aminooxy)acetic acid : A member of the class of hydroxylamines that is acetic acid substituted at postion 2 by an aminooxy group. It is a compound which inhibits aminobutyrate aminotransferase activity in vivo, resulting in increased levels of gamma-aminobutyric acid in tissues. Aminooxyacetic Acid: A compound that inhibits aminobutyrate aminotransferase activity in vivo, thereby raising the level of gamma-aminobutyric acid in tissues. | amino acid; hydroxylamines; monocarboxylic acid | anticonvulsant; EC 2.6.1.19 (4-aminobutyrate--2-oxoglutarate transaminase) inhibitor; EC 4.2.1.22 (cystathionine beta-synthase) inhibitor; nootropic agent |
| salicylic acid | Scalp: The outer covering of the calvaria. It is composed of several layers: SKIN; subcutaneous connective tissue; the occipitofrontal muscle which includes the tendinous galea aponeurotica; loose connective tissue; and the pericranium (the PERIOSTEUM of the SKULL). | monohydroxybenzoic acid | algal metabolite; antifungal agent; antiinfective agent; EC 1.11.1.11 (L-ascorbate peroxidase) inhibitor; keratolytic drug; plant hormone; plant metabolite |
| aurintricarboxylic acid | aurintricarboxylic acid : A member of the class of quinomethanes that is 3-methylidene-6-oxocyclohexa-1,4-diene-1-carboxylic acid in which the methylidene hydrogens are replaced by 4-carboxy-3-hydroxyphenyl groups. The trisodium salt is the biological stain 'chrome violet CG' while the triammonium salt is 'aluminon'. Aurintricarboxylic Acid: A dye which inhibits protein biosynthesis at the initial stages. The ammonium salt (aluminon) is a reagent for the colorimetric estimation of aluminum in water, foods, and tissues. | monohydroxybenzoic acid; quinomethanes; tricarboxylic acid | fluorochrome; histological dye; insulin-like growth factor receptor 1 antagonist |
| mesalamine | mesalamine : A monohydroxybenzoic acid that is salicylic acid substituted by an amino group at the 5-position. Mesalamine: An anti-inflammatory agent, structurally related to the SALICYLATES, which is active in INFLAMMATORY BOWEL DISEASE. It is considered to be the active moiety of SULPHASALAZINE. (From Martindale, The Extra Pharmacopoeia, 30th ed) | amino acid; aromatic amine; monocarboxylic acid; monohydroxybenzoic acid; phenols | non-steroidal anti-inflammatory drug |
| penicillamine | penicillamine : An alpha-amino acid having the structure of valine substituted at the beta position with a sulfanyl group. Penicillamine: 3-Mercapto-D-valine. The most characteristic degradation product of the penicillin antibiotics. It is used as an antirheumatic and as a chelating agent in Wilson's disease. | non-proteinogenic alpha-amino acid; penicillamine | antirheumatic drug; chelator; copper chelator; drug allergen |
| nitroxoline | nitroxoline : A monohydroxyquinoline in which the hydroxy group is positioned at C-8 with a nitro group trans to it at C-5. nitroxoline: structure in Merck Index, 9th ed, #6475; RN given refers to parent cpd | C-nitro compound; monohydroxyquinoline | antifungal agent; antiinfective agent; antimicrobial agent; renal agent |
| olsalazine | olsalazine : An azobenzene that consists of two molecules of 4-aminosalicylic acid joined by an azo linkage. A prodrug for mesalazine, an anti-inflammatory drug, it is used (as the disodium salt) in the treatment of inflammatory bowel disease. olsalazine: cpd with 2 salicylate molecules linked together by an azo bond | azobenzenes; dicarboxylic acid | non-steroidal anti-inflammatory drug; prodrug |
| methyldopa | alpha-methyl-L-dopa : A derivative of L-tyrosine having a methyl group at the alpha-position and an additional hydroxy group at the 3-position on the phenyl ring. Methyldopa: An alpha-2 adrenergic agonist that has both central and peripheral nervous system effects. Its primary clinical use is as an antihypertensive agent. | L-tyrosine derivative; non-proteinogenic L-alpha-amino acid | alpha-adrenergic agonist; antihypertensive agent; hapten; peripheral nervous system drug; sympatholytic agent |
| 6-amino-7-chloro-5,8-dioxoquinoline | 6-amino-7-chloro-5,8-dioxoquinoline: quinone structure important in this cpd; structure | ||
| kalafungin | kalafungin: nanaomycin D from Streptomyces rosa & is enantiomer of kalafungin; RN given refers to (3aR-(3aalpha,5alpha,11balpha))-isomer; see also nanaomycin C; structure of kalafungin in first source; structure of nanaomycin in second source | ||
| nsc228155 | |||
| agathisflavone | agathisflavone : A biflavonoid that is obtained by oxidative coupling of two molecules of apigenin resulting in a bond between positions C-6 and C-8 of the two chromene rings. agathisflavone: bis-apigenin coupled at 6 and 8 positions; isolated from the plant Canarium manii; has hepatoprotective activity against carbon tetrachloride-induced hepatotoxicity | biaryl; biflavonoid; hydroxyflavone | antineoplastic agent; antiviral agent; hepatoprotective agent; metabolite |
| cupressuflavone | cupressuflavone : A biflavonoid that is obtained by oxidative coupling of two molecules of apigenin resulting in a bond between positions C-8 of the two chromene rings respectively. Isolated from Cupressus sempervirens and Juniperus occidentalis, it exhibits free radical scavenging and antielastase activities. cupressuflavone: from Cupressus macrocarpa; structure in first source | biflavonoid; hydroxyflavone; ring assembly | EC 3.4.21.37 (leukocyte elastase) inhibitor; metabolite; radical scavenger |
| podocarpusflavone a | podocarpusflavone A: isolated from Podocarpus imbricatus | flavonoid oligomer | |
| aminoethoxyvinylglycine | aminoethoxyvinylglycine: RN given for (S-(E))-isomer |