In molecular biology, the prokaryotic riboflavin biosynthesis protein is a bifunctional enzyme found in 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...

.

Riboflavin

Riboflavin

Riboflavin, also known as vitamin B2 or additive E101, is an easily absorbed micronutrient with a key role in maintaining health in humans and animals. It is the central component of the cofactors FAD and FMN, and is therefore required by all flavoproteins. As such, vitamin B2 is required for a...

 is converted into catalytically active cofactors

Cofactor (biochemistry)

A cofactor is a non-protein chemical compound that is bound to a protein and is required for the protein's biological activity. These proteins are commonly enzymes, and cofactors can be considered "helper molecules" that assist in biochemical transformations....

 (FAD

FAD

In biochemistry, flavin adenine dinucleotide is a redox cofactor involved in several important reactions in metabolism. FAD can exist in two different redox states, which it converts between by accepting or donating electrons. The molecule consists of a riboflavin moiety bound to the phosphate...

 and FMN

FMN

FMN may refer to several things:* Flavin mononucleotide.* Forsvarsministeriet, the Danish Ministry of Defence.* Four Corners Regional Airport outside Farmington, New Mexico, its IATA airport code.* Fluid Music....

) by the actions of riboflavin kinase

Riboflavin kinase

In enzymology, a riboflavin kinase is an enzyme that catalyzes the chemical reactionThus, the two substrates of this enzyme are ATP and riboflavin, whereas its two products are ADP and FMN....

 , which converts it into FMN, and FAD synthetase , which adenylates

Adenylation

Adenylylation is a posttranslational modification that can occur to molecules such as tyrosine residues. Adenylylation involves a phosphodiester bond between a hydroxyl group of the molecule undergoing adenylylation and the phosphate group of the adenosine monophosphate nucleotide Adenylylation is...

 FMN to FAD. Eukaryotes usually have two separate enzymes, while most prokaryotes have a single bifunctional protein

Protein

Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...

 that can carry out both catalyses, although exceptions occur in both cases. While eukaryotic monofunctional riboflavin kinase is orthologous to the bifunctional prokaryotic 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...

, the monofunctional FAD synthetase differs from its prokaryotic

Prokaryote

The prokaryotes are a group of organisms that lack a cell nucleus , or any other membrane-bound organelles. The organisms that have a cell nucleus are called eukaryotes. Most prokaryotes are unicellular, but a few such as myxobacteria have multicellular stages in their life cycles...

 counterpart, and is instead related to the PAPS-reductase family. The 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...

l FAD synthetase that is part of the bifunctional enzyme has remote similarity to nucleotidyl transferases and, hence, it may be involved in the adenylylation reaction of FAD synthetases.