This view shows enzymes only for those organisms listed below, in the list of taxa known to possess the pathway. If an enzyme name is shown in bold, there is experimental evidence for this enzymatic activity.
|Superclasses:||Biosynthesis → Metabolic Regulators Biosynthesis → Nitric Oxide Biosynthesis|
Expected Taxonomic Range: Viridiplantae
The discovery of nitric oxide (NO) as a crucial signal in plants has enhanced and redirected our understanding of many processes in plant physiology. There has been a surge in investigative studies to understand the biosynthesis of NO in both plants and animals. Plant NO biosynthesis appears to be more complex than animal NO synthesis, as it includes nitrite and L-arginine-dependent mechanisms. In animals, NO synthases are the main sources of nitric oxide, these complex enzymes oxidize L-arginine to nitric oxide and L-citrulline [Crawford06]. The plant NOS isolated from Arabidopsis thaliana has no sequence similarity with animal NOS, but its role in NO production has been demonstrated. The Arabidopsis mutant AtNOS1 encodes a distinct nitric oxide synthase that regulates growth and hormonal signaling in plants [Guo03].
Evidence has accumulated that the NOS in plants are targeted to plastids and are required for ribosome functions, and also indicates it to be a GTPase [Gas09]. In other studies, it was demonstrated that the disruption of NOS dependent NO synthesis is associated with salt tolerance in plants like Arabidopsis thaliana [Zhao07].
In Solanum lycopersicum, NOS generated NO acts downstream of auxin and is involved in regulating Fe-deficiency-induced responses as shown in this study [Jin11]. However, the exact relationship between NO and IAA is not yet clear.
Variants: L-citrulline-nitric oxide cycle
Gas09: Gas E, Flores-Perez U, Sauret-Gueto S, Rodriguez-Concepcion M (2009). "Hunting for plant nitric oxide synthase provides new evidence of a central role for plastids in nitric oxide metabolism." Plant Cell 21(1);18-23. PMID: 19168714
Jin11: Jin CW, Du ST, Shamsi IH, Luo BF, Lin XY (2011). "NO synthase-generated NO acts downstream of auxin in regulating Fe-deficiency-induced root branching that enhances Fe-deficiency tolerance in tomato plants." J Exp Bot 62(11);3875-84. PMID: 21511908
Calaycay96: Calaycay JR, Kelly TM, MacNaul KL, McCauley ED, Qi H, Grant SK, Griffin PR, Klatt T, Raju SM, Nussler AK, Shah S, Weidner JR, Williams HR, Wolfe GC, Geller DA, Billiar TR, MacCoss M, Mumford RA, Tocci MJ, Schmidt JA, Wong KK, Hutchinson NI (1996). "Expression and immunoaffinity purification of human inducible nitric-oxide synthase. Inhibition studies with 2-amino-5,6-dihydro-4H-1,3-thiazine." J Biol Chem 271(45);28212-9. PMID: 8910438
Forstermann94: Forstermann U, Closs EI, Pollock JS, Nakane M, Schwarz P, Gath I, Kleinert H (1994). "Nitric oxide synthase isozymes. Characterization, purification, molecular cloning, and functions." Hypertension 23(6 Pt 2);1121-31. PMID: 7515853
Garvey94: Garvey EP, Tuttle JV, Covington K, Merrill BM, Wood ER, Baylis SA, Charles IG (1994). "Purification and characterization of the constitutive nitric oxide synthase from human placenta." Arch Biochem Biophys 311(2);235-41. PMID: 7515611
Sherman93: Sherman PA, Laubach VE, Reep BR, Wood ER (1993). "Purification and cDNA sequence of an inducible nitric oxide synthase from a human tumor cell line." Biochemistry 32(43);11600-5. PMID: 7692964
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