# Preparation and analysis of quinoa active protein (QAP) and its mechanism of inhibiting Candida albicans from a transcriptome perspective

## TL;DR

This study isolates quinoa active protein (QAP) and shows it inhibits Candida albicans growth by disrupting cell structures and metabolic processes.

## Contribution

The study identifies 18 active quinoa proteins and reveals their antifungal mechanism against Candida albicans through transcriptome analysis.

## Key findings

- QAP inhibits Candida albicans with a minimum inhibitory concentration of 182 µg/mL.
- QAP disrupts hyphal development, cell wall integrity, and oxidative phosphorylation in Candida albicans.
- Proteomic and transcriptomic analyses reveal 18 active quinoa proteins and their antifungal targets.

## Abstract

The globe cultivation and industrial production of quinoa have been steadily increasing. Nevertheless, the full potential of quinoa’s nutritional and economic benefits remains underexploited. This study investigates the isolation and purification of quinoa active protein (QAP) through the precipitation method using ammonium sulfate from a phosphate extraction solution. The purification process involved gel filtration chromatography with Sephadex G-75 and Sephadex G-50 columns to obtain QAP fractions exhibiting inhibitory effects against Candida albicans (C. albicans). A comprehensive series of experiments was undertaken to examine the antifungal properties of these fractions. Proteomic analysis was employed to elucidate the composition of the active proteins. Furthermore, the activities of succinate dehydrogenase, Ca2+-Mg2+-ATPase, and catalase in C. albicans following treatment with QAP were quantified using an enzyme-linked immunosorbent assay. The effects of QAP on the cell morphology of C. albicans cultured on Spider agar medium was further investigated using scanning electron microscopy (SEM). Furthermore, RNA-seq analysis was conducted to investigate the alterations in gene expression in C. albicans cells subjected to QAP treatment. To elucidate the functional significance of these expression changes, Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analyses were performed. Quantitative real-time polymerase chain reaction was subsequently employed to validate the observed changes in gene expression. Our findings demonstrate that QAP exhibits inhibitory effects against C. albicans, with a minimum inhibitory concentration of 182 µg/mL. Through proteomic analysis, a definitive set of 18 active quinoa proteins was identified. At the molecular level, genes associated with hyphal development, cell wall and membrane integrity, cellular respiration, and energy metabolism were found to be enriched. Protein–protein interaction (PPI) analysis revealed that these QAP inhibit the growth of C. albicans hyphae, compromise cell wall and membrane integrity, and suppress oxidative phosphorylation. These disruptions collectively impair normal cellular metabolic activities, thereby exerting an inhibitory effect on C. albicans.