Soluble and insoluble α-glucan synthesis in yeast by enzyme suites derived exclusively from maize endosperm

• DOI: 10.1093/plphys/kiad358
• Publication Date: 2023-06-20T20:09:35Z
• Authors: Susan K Boehlein; Barbara Pfister; Tracie A Hennen-B...; Chun Liu; Maximilian Ritter; L Curtis Hannah; Samuel C Zeeman; Marcio F R Resende; Alan M Myers
• Keywords: 2. Zero hunger; Starch Synthase; Starch; Saccharomyces cerevisiae; Zea mays; Glucans; Endosperm; Research Article; Plant Proteins

Molecular mechanisms that distinguish the synthesis of semi-crystalline α-glucan polymers found in plant starch granules from water-soluble by nonplant species are not well understood. To address this, biosynthetic enzymes maize (Zea mays L.) endosperm were isolated a reconstituted environment using yeast (Saccharomyces cerevisiae) as test bed. Ninety strains constructed containing unique combinations 11 synthetic transcription units specifying synthase (SS), phosphorylase (PHO), branching enzyme (SBE), or isoamylase-type debranching (ISA). Soluble and insoluble branched α-glucans accumulated varying proportions depending on suite, with ISA function stimulating distribution into form. Among SS isoforms, SSIIa, SSIII, SSIV individually supported accumulation glucan polymer. Neither SSI nor SSV alone produced polymers; however, synergistic effects demonstrated both isoforms can stimulate accumulation. PHO did support production itself, but it had either positive negative polymer content which combination thereof was present. The complete suite generated particles resembling native size, shape, crystallinity. Ultrastructural analysis revealed hierarchical assembly starting subparticles approximately 50 nm diameter coalesce discrete structures 200 diameter. These assembled superstructures up to 4 μm length filling most cytosol. essential for formation such particles, their abundance increased dramatically presence.