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Uridine triphosphate is a nucleotide that is used in the DNA transcription during which information of a gene is transcribed into mRNA. In addition to the use of UTP as a source of cellular energy (energy currency but not as common as ATP), it is also capable of providing an equivalent amount of energy to perform reactions such as activation of substrates, phosphorylation of metabolites by phosphate group transfer.
Biochemical processes that require UTP
Central Dogma of the Molecular Biology; the flow of information from DNA to RNA and then RNA to polypeptide (functional and structural molecules) have three steps. These are 1) Replication; in which DNA is duplicated to another copy of DNA during the process of cell division, 2) Transcription; during which a segment of DNA called as a gene is transcribed into mRNA, and 3) Translation; during which mRNA is translated into a polypeptide.
During Transcription, UTP is incorporated into the RNA in place of TTP. However, transcription alone is not only the process that requires UTP, but there are also some other processes that require this nucleotide. These processes are described below.
Glycogen synthesis is the anabolic pathway in which glycogen is synthesized from glucose residues to store the carbohydrate for future use. It requires activated glucose residue and is catalyzed by two enzymes; glycogen synthase and branching enzyme. This process requires UTP to activate the glucose residue before enzymes catalyze the condensation reaction to form glycogen. A glucose molecule is first phosphorylated to Glucose-6-Phosphate catalyzed by Glucokinase and then Glucose-6-Phosphate is converted into the Glucose-1-Phosphate catalyzed by Phosphoglucomutase.
Glucose-1-Phosphate then reacts with UTP to form activated UDP-glucose molecule catalyzed by UDP-Glucose Phosphorylase. Thus activated UDP-glucose residues are utilized to synthesize glycogen. Glycogen synthesis is, therefore, an energy-requiring process and occurs in the cytosol only when there is sufficient energy to store an excess of glucose residues in the form of glycogen for future use.
Similarly, in glycolipids biosynthesis and glycoproteins biosynthesis, UTP is required to activate the sugar residues like Galactose, Glucose, Mannose and some sugar derivatives like N-acetyl Neuraminic acids and N-acetyl Glucosamine. Before being utilized, these molecules are phosphorylated and then activated by reacting with UTP to form UDP-derivatives. These activated molecules are used in some of the steps of the pathways.
Thus, UTP nucleotides have great importance not only in the DNA transcription but also in other biochemical pathways and it can also act as energy currency in the same way as ATP does.