A novel PMA synthetase is the key enzyme for polymalate biosynthesis and its gene is regulated by a calcium signaling pathway in Aureobasidium melanogenum ATCC62921

Abstract

It has been well known that poly(β-l-malic acid)(PMA) has many potential applications. However, it is still completely unknown how PMA is biosynthesized in Aureobasidium spp. In this study, it was found that malic acid from TCA cycle was the main source for PMA biosynthesis. Especially, the novel PMA synthetase encoded by the PMAs gene, a non-ribosomal peptide synthetase (NRPS) containing A like domain, T domain and C like domain was the key enzyme for polymerization of malate into PMA. Therefore, abolishment of the PMAs gene encoding the novel PMA synthetase rendered the mutant ΔPMAs-3 totally to lose the ability to synthesize any PMA and complementation of the PMAs gene partially restored PMA biosynthesis, but the mutant could grow normally on the YPD plate and in the PMA medium with CaCO_3. The transcriptional activator Crz1 in the Ca²⁺-signal pathway controlled expression of the PMAs gene and PMA biosynthesis. The complete elucidation of the PMA biosynthesis pathway and its regulation was of significant for a deeper understanding of detailed yeast-like fungal PMA synthesis, metabolic engineering and molecular editing for modifying PMA biosynthesis and its physicochemical properties.

Keywords: Aureobasidium; Ca(2+) signaling pathway; PMA synthetase; Poly(β-l-malic acid).