citrulline-nitric oxide cycle
Pathway
Source
Taxonomic Scope
organism_specific
Taxonomy
Category
pathway
Dates
- Create:2019-01-17
- Modify:2022-05-18
Description
General Background
NITRIC-OXIDE (NO) is the active moiety of the endothelium-derived relaxing factor. In the vasculature NO relaxes smooth muscle and inhibits platelet and leukocyte adhesion. Outside the vasculature, NO participates in the immunologic response to infection. It serves as a neurotransmitter and plays an important role in cell signaling in the nervous system, and in synaptic plasticity.
Nitric oxide synthases are a family of enzymes responsible for the NADPH dependent synthesis of nitric oxide from ARG and oxygen in the PWY-4983.
About this Pathway
NITRIC-OXIDE can be synthesized by three nitric oxide synthases from ARG generating L-CITRULLINE as a by-product. In this cycle, arginine forms NO and citrulline, and is subsequently regenerated from citrulline by the action of the enzymes CPLX-6641 and CPLX-6661. These two enzymes are shared with the PWY-4984. Citrulline is also required in PWY-4921.
The citrulline-NO cycle functions in many different types of cells. It has been demonstrated in epithelial cells, chondrocytes, endothelial cells, macrophages and neurons [PMID: 2236071][PMID: 1731766].
The enzymes CPLX-6641 and CPLX-6661 confer cells with the capacity to produce NO without the need for exogenous arginine. In vascular smooth muscle cells CPLX-6661 is constitutively expressed but CPLX-6641 is inducible by cytokines and bacterial endotoxin [PMID: 7511585].
- BioCycLICENSEIncludes BioCyc pathway/genome databases under license from SRI Internationalhttps://bioinformatics.ai.sri.com/ptools/licensing/all-reg.shtml
- PubChem
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