Biosynthesis of isoxazolin-5-one and 3-nitropropanoic acid containing glucosides in juvenile Chrysomelina.

Tobias Becker,Wilhelm Boland,Kerstin Ploss

doi:10.1039/c6ob00899b

Abstract

Stable-isotope-labeled precursors were used to establish the biosynthetic pathway leading from β-alanine towards isoxazolin-5-one glucoside 1 and its 3-nitropropanoate (3-NPA) ester 2 in Chrysomelina larvae. Both structural elements originate from sequestered plant-derived β-alanine or from propanoyl-CoA that is derived from the degradation of some essential amino acids, e.g. valine. β-Alanine is converted into 3-NPA and isoxazolinone 5 by consecutive oxidations of the amino group of β-Ala. Substituting the diphospho group of α-UDP-glucose with 5 generates the isoxazolin-5-one glucoside 1, which serves in the circulating hemolymph of the larva as a platform for esterification with 3-nitropropanoyl-CoA. The pathway was validated with larvae of Phaedon cochleariae, Chrysomela populi as well as Gastrophysa viridula.

Highlights

Leaf beetles of the subtribe Chrysomelina[1,2,3,4,5,6,7,8] and a number of legume plants[9,10,11,12] produce the glucosides 1 and 2 (Fig. 1)
Both structural elements originate from sequestered plant-derived β-alanine or from propanoyl-CoA that is derived from the degradation of some essential amino acids, e.g. valine. β-Alanine is converted into 3-NPA and isoxazolinone 5 by consecutive oxidations of the amino group of β-Ala
It is important to note that the oxidation products of β-alanine serve as precursors for both 3-NPA and the isoxazolinone 1

Summary

Introduction

Leaf beetles of the subtribe Chrysomelina[1,2,3,4,5,6,7,8] and a number of legume plants[9,10,11,12] produce the glucosides 1 and 2 (Fig. 1). Stable-isotope-labeled precursors were used to establish the biosynthetic pathway leading from β-alanine towards isoxazolin-5-one glucoside 1 and its 3-nitropropanoate (3-NPA) ester 2 in Chrysomelina larvae.

Results

Conclusion