Abstract
Phytoene desaturase (CrtI, E.C. 1.3.99.31) shows variable desaturation activity, thereby introducing different numbers of conjugated double bonds (CDB) into the substrate phytoene. In particular, Rhodobacter sphaeroides CrtI is known to introduce additional 6 CDBs into the phytoene with 3 CDBs, generating neurosporene with 9 CDBs. Although in-depth studies have been conducted on the function and phylogenetic evolution of CrtI, little information exists on its range of CDB-introducing capabilities. We investigated the relationship between the structure and CDB-introducing capability of CrtI. CrtI of R. sphaeroides KCTC 12085 was randomly mutagenized to produce carotenoids of different CDBs (neurosporene for 9 CDBs, lycopene for 11 CDBs, and 3,4-didehydrolycopene for 13 CDBs). From six CrtI mutants producing different ratios of neurosporene/lycopene/3,4-didehydrolycopene, three amino acids (Leu163, Ala171, and Ile454) were identified that significantly determined carotenoid profiles. While the L163P mutation was responsible for producing neurosporene as a major carotenoid, A171P and I454T produced lycopene as the major product. Finally, according to the in silico model, the mutated amino acids are gathered in the membrane-binding domain of CrtI, which could distantly influence the FAD binding region and consequently the degree of desaturation in phytoene.
Highlights
Edinson Yara-Varón and Carotenoids are a diverse group of colored isoprenoid derivatives that play distinct roles in nature [1]
More than 800 different carotenoids are synthesized in photosynthetic microorganisms, plants, and animals [2]
Occurring carotenoids and their biosynthetic pathways are classified as C30, C40, and C50 based on the carbon numbers of their backbone structures [3]
Summary
Edinson Yara-Varón and Carotenoids are a diverse group of colored isoprenoid derivatives that play distinct roles in nature [1]. Carotenoids serve several biological functions, including in coloration, photoprotective activities, and light harvesting, and are the precursors for several plant hormones [4,5,6]. Carotenoids are widely used in the food, medical, pharmaceutical, and cosmetic industries as colorants and functional ingredients [7,8]. Despite the structural diversity and commercial importance of carotenoids, only a few simplestructured carotenoids, such as β-carotene and lycopene, are produced commercially by chemical synthesis or isolation. Their increasing industrial importance has led to renewed efforts to develop bioprocesses for the production of diverse carotenoids [8,9,10]
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