YUCCA A Newly Characterized FMO Catalyzes Key Intermediate in Auxin Biosynthesis

 

YUCCA a newly characterized FMO involved in auxin biosynthesis: Sequence analysis of yucca showed that both binding motifs, FAD and NADPH were present in the protein. To prove that YUCCA performed a FMO type function, a likely substrate, tryptamine, was identified. When tryptamine was used in vitro as a substrate for YUCCA, N-hydroxyl tryptamine was identified as a new compound by mass spectrometry. These results suggest that YUCCA catalyzes the N-oxygenation of tryptamine (Figure 12) (Zhoa et al 2001).

Typtamine + O2 + NADPH + H+ ---YUCCA---> N-hydroxyl tryptamine + H2O + NADP+

 Figure 12: YUCCA catalyzes the N-oxygenation of tryptamine

YUCCA and auxin metabolism: YUCCA acts through the tryptophan dependent pathway in auxin biosynthesis by catalyzing the N-oxygenation of tryptamine (Figure 13).

 

Figure 13: YUCCA acts by catalyzing the N-oxygenation of tryptamine in the "mysterious third pathway" (Zhoa et al 2001).

Wildtype and yucca plants were grown on medium containing 5-methyl-tryptophan (5-mt). This compound is toxic to plants because it inhibits tryptophan biosynthesis. Wildtype were unable to grow, but yucca was unaffected by the tryptophan analog (Figure 14).

 

 Figure 14: 5-mt is lethal to wildtype plants

In yucca plants 5-mt was converted into 5-methyl IAA, an active auxin. This experiment showed that YUCCA functions in the tryptophan dependent pathway of auxin biosynthesis (Figure 15) (Zhoa et al 2001).

 

Figure 15: YUCCA utilizes 5-mt to thrive

Home Page	Introduction
Plant Hormones	Auxins
yucca	Flavin Monooxygenase
Conclusion	References