enzymology Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products. A ...

, a dihydrouracil dehydrogenase (NAD+) () is an

enzyme Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products. A ...

that

catalyzes Catalysis () is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst (). Catalysts are not consumed in the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recyc ...

the

chemical reaction A chemical reaction is a process that leads to the IUPAC nomenclature for organic transformations, chemical transformation of one set of chemical substances to another. Classically, chemical reactions encompass changes that only involve the pos ...

:5,6-dihydrouracil + NAD⁺

\rightleftharpoons

uracil + NADH + H⁺ Thus, the two substrates of this enzyme are

5,6-dihydrouracil Dihydrouracil is an intermediate in the catabolism of uracil. It is the base present in the nucleoside dihydrouridine Dihydrouridine (abbreviated as D, DHU, or UH2) is a pyrimidine nucleoside which is the result of adding two hydrogen atoms to ...

and NAD⁺, whereas its 3 products are

uracil Uracil () (symbol U or Ura) is one of the four nucleobases in the nucleic acid RNA. The others are adenine (A), cytosine (C), and guanine (G). In RNA, uracil binds to adenine via two hydrogen bonds. In DNA, the uracil nucleobase is replaced by ...

, NADH, and H⁺. This enzyme belongs to the family of

oxidoreductase In biochemistry, an oxidoreductase is an enzyme that catalyzes the transfer of electrons from one molecule, the reductant, also called the electron donor, to another, the oxidant, also called the electron acceptor. This group of enzymes usually ut ...

s, specifically those acting on the CH-CH group of donor with NAD+ or NADP+ as acceptor. The systematic name of this enzyme class is 5,6-dihydrouracil:NAD+ oxidoreductase. Other names in common use include dehydrogenase, dihydrouracil, dihydropyrimidine dehydrogenase, dihydrothymine dehydrogenase, pyrimidine reductase, thymine reductase, uracil reductase, and dihydrouracil dehydrogenase (NAD+). This enzyme participates in 3 metabolic pathways:

pyrimidine metabolism Pyrimidine biosynthesis occurs both in the body and through organic synthesis. ''De novo'' biosynthesis of pyrimidine ''De Novo'' biosynthesis of a pyrimidine is catalyzed by three gene products CAD, DHODH and UMPS. The first three enzymes of ...

, beta-alanine metabolism, and

pantothenate and coa biosynthesis Pantothenic acid, also called vitamin B5 is a water-soluble B vitamin and therefore an essential nutrient. All animals require pantothenic acid in order to synthesize coenzyme A (CoA) – essential for fatty acid metabolism – as well as to, ...

References

* EC 1.3.1 NADH-dependent enzymes Enzymes of unknown structure {{1.3-enzyme-stub