Functional Lycopene Cyclase (CruA) in Cyanobacterium, Arthrospira platensis NIES-39, and its Role in Carotenoid Synthesis

Abstract

The genus Arthrospira is filamentous, non-nitrogen-fixing cyanobacteria that is commercially important. We identified the molecular structures of carotenoids in Arthrospira platensis NIES-39. The major carotenoid identified was β-carotene. In addition, the hydroxyl derivatives of β-cryptoxanthin and (3R,3'R)-zeaxanthin were also found to be present. The carotenoid glycosides were identified as (3R,2'S)-myxol 2'-methylpentoside and oscillol 2,2'-dimethylpentoside. The methylpentoside moiety was a mixture of fucoside and chinovoside in an approximate ratio of 1 : 4. Trace amounts of the ketocarotenoid 3'-hydroxyechinenone were also found. Three types of lycopene cyclases have been functionally confirmed in carotenogenesis organisms. In cyanobacteria, the functional lycopene cyclases (CrtL, CruA and CruP) have only been found in four species. In this study, we found that CruA exhibited lycopene cyclase activity in transformed Escherichia coli, which contains lycopene, but CruP exhibited no lycopene cyclase activity and crtL was absent. This is the third cyanobacterial species in which CruA activity has been confirmed. Neurosporene was not a substrate of CruA in E. coli, whereas lycopene cyclases of CrtY (bacteria), CrtL (plants) and CrtYB (fungi) have been reported to convert neurosporene to 7,8-dihydro-β-carotene. β-Carotene hydroxylase (CrtR) was found to convert β-carotene to zeaxanthin in transformed E. coli, which contains β-carotene. Among the β-carotene hydroxylases, bacterial CrtZ and eukaryotic CrtR and BCH have similarities, whereas cyanobacterial CrtR appears to belong to another clade. Based on the identification of the carotenoids and the completion of the entire nucleotide sequence of the A. platensis NIES-39 genome, we propose a biosynthetic pathway for the carotenoids as well as the corresponding genes and enzymes.

Introduction of the Carotenoid Biosynthesis α-Branch Into Synechocystis sp. PCC 6803 for Lutein Production

“…Thus, these data provide further evidence that cruA (sll0147) encodes the lycopene β-cyclase in Synechocystis. In contrast, for the paralog CruP no β-cyclase activity could be proven (Figure 1A; Sugiyama et al, 2017;Sugiyama and Takaichi, 2020). Rather, CruP seems to be involved in ROS scavenging processes (Bradbury et al, 2012).…”

Carotenogenesis in cyanobacteria: CruA/CruP-type and CrtL-type lycopene cyclases

“…This cyclization reaction is catalyzed by lycopene cyclase. Thus far, several types of lycopene cyclases have been confirmed in various organisms including cyanobacteria (Takaichi, 2013;Xiong et al, 2017;Sugiyama et al, 2017). Furthermore, this is the branching point of β-carotene and γ-carotene: from β-carotene, echinenone, zeaxanthin and nostoxanthin are produced; and from γ-carotene, myxol glycoside, ketomyxol glycoside and 2-hycroxymyxol glycoside are produced (Takaichi and Mochimaru, 2007).…”

“…Based on the carotenoid profile of the CruP-deficient mutants, they proposed that the role of CruP should be rather on reducing oxidative damage caused by singlet oxygen. Recently, Sugiyama et al (2017) have reported that CruA in Arthrospira platensis NIES-39 has lycopene cyclase activity, whereas CruP does not, by using lycopene producing E. coli. Furthermore, Xiong et al (2017) found that CruA in Synechocystis sp.…”

Potential of Microalgae Biomass for the Sustainable Production of Bio-commodities

“…leaving room for implementing such technology also in microalgae. In the future, identifying novel candidates(Sugiyama et al 2017;Lao et al 2018) and engineering simoultaneously multiple enzymatic steps in the pathway might strengthen the metabolic flux redirection towards carotenoids synthesis with no secondary effects on cell physiology and the development of effective targeted genome editing approaches is currently opening such possibility(Nymark et al 2016;Banerjee et al 2018).…”