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J Insect Physiol. 2017 Aug;101:91-96. doi: 10.1016/j.jinsphys.2017.07.006. Epub 2017 Jul 18.

Novel tryptophan metabolic pathways in auxin biosynthesis in silkworm.

Author information

1
Department of Food and Life Sciences, Ibaraki University, 3-21-1 Chuo, Ami-machi, Inashiki, Ibaraki 300-0393, Japan.
2
Department of Integrated Biosciences, Graduate School of Frontier Sciences, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa-city, Chiba 277-8567, Japan.
3
Department of Food and Life Sciences, Ibaraki University, 3-21-1 Chuo, Ami-machi, Inashiki, Ibaraki 300-0393, Japan. Electronic address: yoshihito.suzuki.chemeco@vc.ibaraki.ac.jp.

Abstract

In the course of our study of the biosynthetic pathway of auxin, a class of phytohormones, in insects, we proposed the biosynthetic pathway tryptophan (Trp)→indole-3-acetaldoxime (IAOx)→indole-3-acetadehyde (IAAld)→indole-3-acetic acid (IAA). In this study, we identified two branches in the metabolic pathways in the silkworm, possibly affecting the efficiency of IAA production: Trp→indole-3-pyruvic acid→indole-3-lactic acid and IAAld→indole-3-ethanol. We also determined the apparent conversion activities (2.05×10-7UmL-1 for Trp→IAA, 1.30×10-5UmL-1 for IAOx→IAA, and 3.91×10-1UmL-1 for IAAld→IAA), which explain why IAOx and IAAld are barely detectable as either endogenous compounds or metabolites of their precursors. The failure to detect IAAld, even in the presence of an inhibitor of the conversion IAAld→IAA, is explained by a switch in the conversion from IAAld→IAA to IAAld→IEtOH.

KEYWORDS:

Auxin; Biosynthesis; Bombyx mori; Gall formation; Indole-3-acetic acid; Silkworm

PMID:
28733236
DOI:
10.1016/j.jinsphys.2017.07.006
[Indexed for MEDLINE]

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