Orotate phosphoribosyltransferase is an enzyme

Enzyme

Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...

 involved in pyrimidine

Pyrimidine

Pyrimidine is a heterocyclic aromatic organic compound similar to benzene and pyridine, containing two nitrogen atoms at positions 1 and 3 of the six-member ring...

 biosynthesis

Biosynthesis

Biosynthesis is an enzyme-catalyzed process in cells of living organisms by which substrates are converted to more complex products. The biosynthesis process often consists of several enzymatic steps in which the product of one step is used as substrate in the following step...

. It catalyzes the formation of orotidine 5'-monophosphate

Orotidine 5'-monophosphate

Orotidine 5'-monophosphate , also known as orotidylic acid, is a pyrimidine nucleotide which is the last intermediate in the biosynthesis of uridine monophosphate. OMP is formed from orotate and phosphoribosyl pyrophosphate by the enzyme Orotate phosphoribosyltransferaseIn humans, the enzyme UMP...

 (OMP) from orotate and phosphoribosyl pyrophosphate

Phosphoribosyl pyrophosphate

Phosphoribosyl pyrophosphate is a pentosephosphate.It is formed from ribose 5-phosphate by the enzyme ribose-phosphate diphosphokinase.It plays a role in transferring phospho-ribose groups in several reactions:...

. In yeast

Yeast

Yeasts are eukaryotic micro-organisms classified in the kingdom Fungi, with 1,500 species currently described estimated to be only 1% of all fungal species. Most reproduce asexually by mitosis, and many do so by an asymmetric division process called budding...

 and bacteria

Bacteria

Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...

, orotate phospohribosyltransferase is an independent enzyme with a unique gene

Gene

A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...

 coding for the protein, whereas in mammals and other multicellular organisms, the catalytic function is carried out by a domain of the bifunctional enzyme UMP synthase

Uridine monophosphate synthetase

Uridine monophosphate synthetase is the enzyme that catalyses the formation of uridine monophosphate , an energy-carrying molecule in many important biosynthetic pathways...

.