Indolepyruvate pathway for indole-3-acetic acid biosynthesis in Bradyrhizobium elkanii
1996
Minamisawa, K. | Ogawa, K. | Fukuhara, H. | Koga, J.
Indole-3-acetaldehyde (IAAld) was detected in the culture supernatant of Bradyrhizobium elkanii. Deuterium-labelled L-tryptophan (Trp) was incorporated into IAAld and indole-3-acetic acid (IAA), suggesting that B. elkanii produces IAA via IAAld from Trp. In B. elkanii cell suspension, indole-3-pyruvic acid (IPyA) was converted to IAAld, and exogenously added IAAld was rapidly conversed to IAA. Furthermore, the activity of indolepyruvate decarboxylase (IPDC), which catalyzes the decarboxylation of IPyA to produce IAAld and is a key enzyme for IPyA pathway, was detected in B. elkanii cell-free extract. The IPDC activity depended on Mg2+ and thiamine pyrophosphate, cofactors of decarboxylation. This mounting evidence strongly suggests that IAA synthesis occurs via IPyA pathway (Trp leads to IPyA leads to IAAld leads to IAA) in B. elkanii.
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