The variant 'his-box' of the C18-Delta9-PUFA-specific elongase IgASE1 from Isochrysis galbana is essential for optimum enzyme activity

Area of Science:

• Biochemistry
• Molecular Biology
• Marine Biotechnology

Background:

• Fatty acid elongases (FAEs) are key enzymes in lipid metabolism.
• Isochrysis galbana possesses a unique FAE component, IgASE1, with a variant histidine box (his-box).
• The conserved his-box motif in FAEs is critical for enzyme function.

Purpose of the Study:

• To investigate the functional significance of the variant his-box in IgASE1.
• To determine the role of specific amino acid residues in the IgASE1 his-box.
• To elucidate the impact of these variations on enzyme activity and substrate specificity.

Main Methods:

• Site-directed mutagenesis was employed to alter amino acid residues within the IgASE1 his-box.
• Enzyme activity assays were performed to measure the catalytic efficiency of mutant IgASE1 variants.
• Substrate specificity studies were conducted to assess the enzyme's preference for different fatty acids.

Main Results:

• All sequence variations within the IgASE1 his-box compared to consensus sequences were essential for optimal enzyme activity.
• Mutagenesis of the variant residues significantly impacted enzyme activity.
• Substrate specificity remained unaffected by the observed amino acid changes in the his-box.

Conclusions:

• The variant amino acid residues in the IgASE1 his-box are critical for achieving optimal enzyme activity.
• These structural variations do not directly dictate substrate specificity, suggesting other protein regions are involved.
• Understanding these FAE variations provides insights into lipid biosynthesis pathways in marine microalgae.