IMP biosynthetic process

Definition

Target type: biologicalprocess

The chemical reactions and pathways resulting in the formation of IMP, inosine monophosphate. [ISBN:0198506732]

The IMP biosynthetic pathway is a fundamental process in nucleotide metabolism, essential for the production of purine nucleotides, which serve as building blocks for DNA and RNA. The pathway involves a series of enzymatic reactions that convert the simple precursor molecule PRPP (5-phosphoribosyl-1-pyrophosphate) into inosine monophosphate (IMP), a precursor to both adenine and guanine nucleotides.

The pathway can be broadly divided into two stages:

**Stage 1: Formation of the Purine Ring**
This stage involves the construction of the purine ring structure, starting with PRPP and gradually adding nitrogen and carbon units from various sources. The key enzymes involved are:
* **PRPP amidotransferase:** This enzyme catalyzes the first committed step in the pathway, converting PRPP to phosphoribosylamine.
* **Glycinamide ribonucleotide (GAR) synthetase:** This enzyme adds glycine to phosphoribosylamine to form glycinamide ribonucleotide (GAR).
* **GAR transformylase:** This enzyme adds formyl group to GAR to produce formylglycinamide ribonucleotide (FGAR).
* **FGAM synthetase:** This enzyme adds glutamine to FGAR to produce formylglycinamidine ribonucleotide (FGAM).
* **AIR synthetase:** This enzyme adds a second formyl group to FGAM to produce aminoimidazole ribonucleotide (AIR).
* **CAIR synthetase:** This enzyme adds aspartate to AIR to form carboxyaminoimidazole ribonucleotide (CAIR).
* **SAICAR synthetase:** This enzyme adds carbon dioxide to CAIR to form succinylaminoimidazole carboxamide ribonucleotide (SAICAR).
* **AICAR transformylase:** This enzyme adds a formyl group to SAICAR to produce aminoimidazole carboxamide ribonucleotide (AICAR).

**Stage 2: Conversion to IMP**
This stage involves the conversion of AICAR to IMP through a series of reactions. The key enzymes involved are:
* **AICAR transformylase:** This enzyme adds a formyl group to AICAR to produce formylaminoimidazole carboxamide ribonucleotide (FAICAR).
* **IMP cyclohydrolase:** This enzyme catalyzes the final ring closure reaction, converting FAICAR to IMP.

**Regulation of IMP Biosynthesis:**
The IMP biosynthetic pathway is tightly regulated to ensure proper levels of purine nucleotides. The key regulatory enzymes are PRPP amidotransferase and IMP cyclohydrolase. These enzymes are subject to feedback inhibition by the end products of the pathway, such as AMP and GMP. This feedback regulation prevents the accumulation of purine nucleotides and conserves cellular resources.

**Importance of IMP Biosynthesis:**
The IMP biosynthetic pathway is essential for life. Purine nucleotides are essential for DNA and RNA synthesis, energy production (ATP), signal transduction (cAMP), and other vital cellular processes. Defects in the pathway can lead to severe genetic disorders, including Lesch-Nyhan syndrome and gout.'
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