Carotenoid hydroxylase from Haematococcus pluvialis: cDNA sequence, regulation and functional complementation

Area of Science:

• Biochemistry
• Algal Biotechnology
• Carotenoid Metabolism

Background:

• Beta-carotene hydroxylase enzymes are key in carotenoid biosynthesis pathways.
• Haematococcus pluvialis is a microalga known for accumulating high levels of astaxanthin.
• Understanding the specific enzymes involved in astaxanthin production is vital for biotechnological applications.

Purpose of the Study:

• To isolate and characterize a beta-carotene hydroxylase cDNA from Haematococcus pluvialis.
• To determine the enzymatic activity and substrate specificity of the isolated enzyme.
• To investigate the role of this enzyme in astaxanthin biosynthesis in H. pluvialis.

Main Methods:

• cDNA isolation and sequencing.
• Heterologous expression and complementation in E. coli.
• Enzymatic assays for substrate conversion.
• Northern blot analysis for gene expression.

Main Results:

• A cDNA encoding a beta-carotene hydroxylase from H. pluvialis was successfully isolated.
• The enzyme demonstrated activity in converting beta-carotene to zeaxanthin and canthaxanthin to astaxanthin.
• Expression analysis showed increased mRNA levels of the enzyme during astaxanthin induction.

Conclusions:

• The characterized H. pluvialis beta-carotene hydroxylase plays a significant role in astaxanthin biosynthesis.
• This enzyme is involved in the conversion of precursors to astaxanthin during cyst cell formation.
• The findings provide insights into the genetic basis of astaxanthin accumulation in H. pluvialis.