Abstract
Haematococcus pluvialis is widely distributed in the world and well known as the richest natural source of astaxanthin that is a strong antioxidant with excellent commercial value. The pathway of astaxanthin biosynthesis in H. pluvialis has been documented as an enzymatic reaction. Several enzymes have been reported, but their isoforms or homologs have not been investigated genome-wide. To better understand the astaxanthin biosynthesis pathway in H. pluvialis, eight candidates of the geranylgeranyl pyrophosphate synthase gene (HpGGPPS) predicted from Iso-seq data were isolated in this study. The length of coding region of these candidates varied from 960 bp to 1272 bp, composing of 7–9 exons. The putative amino acids of all candidates composed the signature domain of GGPPS gene. However, the motifs in the domain region are varied, indicating different bio-functions. Phylogenetic analysis revealed eight candidates can be clustered into three groups. Only two candidates in Group1 encode the synthase participating in the astaxanthin formation. The yield of astaxanthin from these two candidates, 7.1 mg/g (DW) and 6.5 mg/g (DW) respectively, is significant higher than that from CrtE (2.4 mg/g DW), a GGPPS gene from Pantoea ananatis. This study provides a potential productive pathway for astaxanthin synthesis.
Highlights
Astaxanthin (C40 H52 O4 ), a keto-carotenoid, has been well known as super vitamin E due to its hydroxyl and ketone functional groups and multiple conjugated double bonds that can reduce the reactive oxidizing molecule
Using three reported GGPPS genes of H. pluvialis retrieved from Genbank
Thereby, the topic of improving astaxanthin production from natural sources is attractive for the industry
Summary
Astaxanthin (C40 H52 O4 ), a keto-carotenoid, has been well known as super vitamin E due to its hydroxyl and ketone functional groups and multiple conjugated double bonds that can reduce the reactive oxidizing molecule. Astaxanthin can be consumed as a dietary supplement or aging related-cosmetics. Astaxanthin has been used as an aquaculture consumption due to its additive of the blood-red color, contributing to over $500 million a year in the market [1]. Astaxanthin can be produced chemically in the factory or naturally from organisms such as the microalga Haematococcus pluvialis and the yeast fungus Xanthophyllomyces dendrorhous [2]. Compared with chemically synthetic astaxanthin from the Wittig reaction using asta-C15-triarylphosphonium salt and the C10-dialdehyde [3], the naturally isolated astaxanthin has 20-times higher antioxidant activity and is capable for human consumption [4,5].
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