Comparative analysis of ZISO-mediated carotenoid biosynthesis in Dunaliella salina and Dunaliella bardawil.

Abstract

Carotenoids are essential natural pigments, and ZISO plays a pivotal role in their biosynthesis. This study compares ZISO enzyme activity in Dunaliella salina and Dunaliella bardawil to evaluate their efficiency in synthesizing 9,9'-di-cis-ζ-carotene. Bacterial strains lacking ZISO (ΔDsZISO, ΔDbZISO) and ZDS (ΔDsZDS, ΔDbZDS) were constructed, and HPLC analysis revealed the accumulation of 9,9'-di-cis-ζ-carotene in ΔDbZDS but not in ΔDsZDS, suggesting that DbZISO exhibits higher activity. Molecular docking and kinetic simulations further indicate that DbZISO forms a more stable complex with 9,9',15-tri-cis-ζ-carotene, with a binding energy lower than that of DsZISO, where the affinity between DbZISO and the substrate is - 13.09 kcal/mol, and the affinity between DsZISO and the substrate is - 12.13 kcal/mol. These results demonstrate that DbZISO is more efficient than DsZISO in catalyzing the isomerization of carotenoid intermediates. This study provides mechanistic insights into ZISO-mediated carotenoid biosynthesis and establishes a foundation for metabolic engineering aimed at enhancing carotenoid production.