SPR

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Sepiapterin reductase

Sepiapterin reductase is an enzyme that in humans is encoded by the SPR gene.

Function

Sepiapterin reductase (7,8-dihydrobiopterin:NADP⁺ oxidoreductase; EC 1.1.1.153) catalyzes the NADPH-dependent reduction of various carbonyl substances, including derivatives of pteridines, and belongs to a group of enzymes called aldo-keto reductases. SPR plays an important role in the biosynthesis of tetrahydrobiopterin.

Reaction

Sepiapterin reductase (SPR) catalyzes the chemical reaction

L-erythro-7,8-dihydrobiopterin + NADP+ sepiapterin + NADPH + H+

Thus, the two substrates of this enzyme are L-erythro-7,8-dihydrobiopterin and NADP⁺, whereas its three products are sepiapterin, NADPH, and a single hydrogen ion (H⁺).

This enzyme belongs to the family of oxidoreductases, to be specific, those acting on the CH-OH group of donor with NAD⁺ or NADP⁺ as acceptor. The systematic name of this enzyme class is 7,8-dihydrobiopterin:NADP⁺ oxidoreductase. This enzyme participates in folate biosynthesis.

Remington Spartan 100

The Remington Spartan 100 is a single-shot, break-action shotgun. It is a variant of a classical Russian shotgun IZh-18 manufactured by Izhevsk Mechanical Plant for export under trademak "Baikal," in Izhevsk, Russia. It is marketed and distributed by Remington.

The Spartan 100 accepts 2¾ inch or 3 inch shotgun shells. It utilizes a cross bolt safety and a selectable ejector or extractor.

Models

SPR100

The standard model SPR100 has a blued receiver, hardwood stock and fore-end, and a fixed choke. It is chambered in 12 gauge with a 28 inch barrel, or in 20 gauge or .410 bore with a 26 inch barrel. It weighs 6½ pounds.

An upgraded version of the SPR100 has a nickel plated receiver, walnut stock and fore-end, and screw-in choke tubes. This variant is a 12 gauge with a 29½ inch barrel.

SPR100 Sporting

The SPR100 Sporting model has a nickel plated receiver, walnut stock and fore-end, and screw-in choke tubes. The barrel is ported to reduce felt recoil.

SPR100 Youth

The SPR100 Youth model is chambered in 20 gauge or .410 bore. It has a 24 inch barrel and weighs 6¼ pounds.