IMP dehydrogenase
Encyclopedia
IMP dehydrogenase 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...

 that converts inosine monophosphate to xanthosine monophosphate
Xanthosine monophosphate
Xanthosine monophosphate is an intermediate in purine metabolism. It is a ribonucleoside monophosphate. It is formed from IMP via the action of IMP dehydrogenase, and it forms GMP via the action of GMP synthase.-Clinical significance:...

:
inosine 5'-phosphate + NAD+
Nicotinamide adenine dinucleotide
Nicotinamide adenine dinucleotide, abbreviated NAD, is a coenzyme found in all living cells. The compound is a dinucleotide, since it consists of two nucleotides joined through their phosphate groups. One nucleotide contains an adenine base and the other nicotinamide.In metabolism, NAD is involved...

 + H2O
Water
Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...

 —–> xanthosine 5'-phosphate
Xanthosine monophosphate
Xanthosine monophosphate is an intermediate in purine metabolism. It is a ribonucleoside monophosphate. It is formed from IMP via the action of IMP dehydrogenase, and it forms GMP via the action of GMP synthase.-Clinical significance:...

 + NADH + H+


The structure of this enzyme is composed of a TIM barrel
TIM barrel
The TIM barrel is a conserved protein fold consisting of eight α-helices and eight parallel β-strands that alternate along the peptide backbone. The structure is named after triosephosphate isomerase, a conserved glycolytic enzyme. TIM barrels are quite common among the conserved protein folds...

 domain with two CBS domain
CBS domain
The CBS domain is a protein domain found in a range of proteins in all species from bacteria to man. It was first identified as a conserved sequence region in 1997 and named after cystathionine beta synthase, one of the proteins it is found in...

s inserted within a loop.

It is inhibited by Mycophenolic acid
Mycophenolic acid
Mycophenolic acid INN or mycophenolate is an immunosuppressant drug used to prevent rejection in organ transplantation. It inhibits an enzyme needed for the growth of T cells and B cells. It was initially marketed as the prodrug mycophenolate mofetil to improve oral bioavailability. More...

.

Examples

Humans express the following two IMP dehydrogenase isozymes:

Further reading

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