Identification of a gene encoding the last step of the L-rhamnose catabolic pathway in Aspergillus niger revealed the inducer of the pathway regulator.

Identification of a gene encoding the last step of the L-rhamnose catabolic pathway in Aspergillus niger revealed the inducer of the pathway regulator.

Microbiol Res. 2020 Feb 07;234:126426

Authors: Chroumpi T, Aguilar-Pontes MV, Peng M, Wang M, Lipzen A, Ng V, Grigoriev IV, Mäkelä MR, de Vries RP

Abstract
In fungi, L-rhamnose (Rha) is converted via four enzymatic steps into pyruvate and L-lactaldehyde, which enter central carbon metabolism. In Aspergillus niger, only the genes involved in the first three steps of the Rha catabolic pathway have been identified and characterized, and the inducer of the pathway regulator RhaR remained unknown. In this study, we identified the gene (lkaA) involved in the conversion of L-2-keto-3-deoxyrhamnonate (L-KDR) into pyruvate and L-lactaldehyde, which is the last step of the Rha pathway. Deletion of lkaA resulted in impaired growth on L-rhamnose, and potentially in accumulation of L-KDR. Contrary to ΔlraA, ΔlrlA and ΔlrdA, the expression of the Rha-responsive genes that are under control of RhaR, were at the same levels in ΔlkaA and the reference strain, indicating the role of L-KDR as the inducer of the Rha pathway regulator.

PMID: 32062364 [PubMed – as supplied by publisher]

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