Biosynthesis of 2-acetyl-1-pyrroline in rice calli cultures: Demonstration of 1-pyrroline as a limiting substrate

• Published in: Food chemistry Vol. 197; no. Pt A; pp. 965 - 971
• Main Authors: Poonlaphdecha, Janchai, Gantet, Pascal, Maraval, Isabelle, Sauvage, François-Xavier, Menut, Chantal, Morère, Alain, Boulanger, Renaud, Wüst, Matthias, Gunata, Ziya
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 15.04.2016; Elsevier
• Subjects: 1-Pyrroline; 13C-labelled precursors; 2-Acetyl-1-pyrroline; Biosynthesis; callus; callus culture; Food and Nutrition; Fragrant rice; glucose; heat treatment; Life Sciences; Odorants - analysis; Oryza - metabolism; Plant Extracts - metabolism; Proline; Pyrroles - metabolism; rice; Rice callus; sodium; sodium acetate; stable isotopes; 13C-labelled precursors; 2-Acetyl-1-pyrroline; 1-Pyrroline; Fragrant rice; Proline; Biosynthesis; Rice callus; C-labelled precursors; proline; enzyme; 1-pyrroline; fragrant rice; rice callus; biosynthesis; c-13-labelled precursors; biosynthèse; 2-acetyl-1-pyrroline; riz parfumé
• ISSN: 0308-8146; 1873-7072
• DOI: 10.1016/j.foodchem.2015.11.060

•1-Pyrroline is a limiting factor in the formation of 2-acetyl-1-pyrroline, key flavour compound in fragrant rice.•When 1-pyrroline is available in non-fragrant rice, the level of 2-acetyl-1-pyrroline may reach that of fragrant rice.•Acetylation of 1-pyrroline ring seems not to be a limiting factor in the formation of 2-acetyl-1-pyrroline.•Thanks to labelling experiments, acetyl CoA was proposed as a good candidate for acetylation of the 1-pyrroline ring. The role of 1-pyrroline was studied via feeding experiments using rice calli cultures to gain further insight into the key steps of 2-acetyl-1-pyrroline (2AP) biosynthesis in rice. The origin of the acetyl donor was also studied through stable isotope labelled substrates. Incubation of fresh calli from a fragrant rice variety (Aychade) and a non-fragrant variety (Gladio×Fidji K2) with 1-pyrroline led to a significant increase in 2AP in both varieties. Importantly, the amount of 2AP in the non-fragrant variety could be greatly enhanced by this supplementation. When rice calli were fed with increasing levels of 1-pyrroline, 2AP levels increased accordingly. Our data show that 1-pyrroline is a limiting factor for 2AP synthesis in rice. Heat treatment of calli suggested that 1-pyrroline might be enzymatically acetylated. The presence of labelled 2AP in calli supplemented with [U-13C]glucose, sodium acetate (1,2-13C2) and sodium octanoate (1,2,3,4-13C4) suggested that these compounds are possible candidates for acetyl group-donors of 2AP, predominately in the form of intact labelled 13C2-units.