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Reference.org
Stearoyl-CoA 9-desaturase
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<p>Stearoyl-CoA desaturase (Δ-9-desaturase or SCD-1) is an endoplasmic reticulum enzyme that catalyzes the rate-limiting step in the formation of <a href="/facts/Monounsaturated_fat/87HcP11s">monounsaturated fatty acids</a> (MUFAs), specifically <a href="/facts/Oleic_acid/NeVuHTbe">oleate</a> and <a href="/facts/Palmitoleic_acid/aUrAYB0T">palmitoleate</a> from <a href="/facts/Stearoyl-CoA/wNh77Pqt">stearoyl-CoA</a> and <a href="/facts/Palmitoyl-CoA/vlVVPJpU">palmitoyl-CoA</a>. Oleate and palmitoleate are major components of membrane phospholipids, cholesterol esters and alkyl-diacylglycerol. In humans, the enzyme is present in two isoforms, encoded respectively by the <i>SCD1</i> and <i>SCD5</i> genes. </p><p>Stearoyl-CoA desaturase-1 is a key <a href="/facts/Enzyme/DSI1Fh7y">enzyme</a> in <a href="/facts/Fatty_acid_metabolism/Se3rnCT8">fatty acid metabolism</a>. It is responsible for forming a <a href="/facts/Double_bond/qDemMn0c">double bond</a> in <a href="/facts/Stearoyl-CoA/wNh77Pqt">stearoyl-CoA</a>. This is how the <a href="/facts/Monounsaturated_fatty_acid/87HcP11s">monounsaturated fatty acid</a> <a href="/facts/Oleic_acid/NeVuHTbe">oleic acid</a> is produced from the <a href="/facts/Saturated_fatty_acid/8pvw306D">saturated fatty acid</a>, <a href="/facts/Stearic_acid/ajnXYFo9">stearic acid</a>. </p><p>A series of <a href="/facts/Redox/Pyd5RVcj">redox</a> reactions, during which two electrons flow from <a href="/facts/Nicotinamide_adenine_dinucleotide/BHdLW925">NADH</a> to flavoprotein cytochrome b5, then to the electron acceptor cytochrome b5 as well as molecular oxygen introduces a single double bond within a row of methylene fatty acyl-CoA substrates. The complexed enzyme adds a single double bond between the C9 and C10 of long-chain <a href="/facts/Acyl-CoA-binding_protein/pCnW8txy">acyl-CoAs</a> from de-novo synthesis. </p><p>This enzyme belongs to the family of <a href="/facts/Oxidoreductase/neW0G5D4">oxidoreductases</a>, specifically those acting on paired donors, with O2 as oxidant and incorporation or reduction of oxygen. The oxygen incorporated need not be derived from O2 with oxidation of a pair of donors resulting in the reduction of O to two molecules of water. The <a href="/facts/List_of_enzymes/w2RP6EwU">systematic name</a> of this enzyme class is <i>stearoyl-CoA,ferrocytochrome-b5:oxygen oxidoreductase (9,10-dehydrogenating)</i>. This enzyme participates in polyunsaturated fatty acid biosynthesis and PPAR signaling pathway. It employs one <a href="/facts/Cofactor_(biochemistry)/AGo0PCUU">cofactor</a>, <a href="/facts/Iron/QK1JYy8E">iron</a>. </p>