Catalytic properties of an expressed and purified higher plant type ζ- carotene desaturase from Capsicum annuum

Abstract

The ζ-carotene desaturase from Capsicum annuum (EC 1.14.99.-) was expressed in Escherichia coli, purified and characterized biochemically. The enzyme acts as a monomer with lipophilic quinones as cofactors. K(m) values for the substrate ζ-carotene or the intermediate neurosporene in the two- step desaturation reaction are almost identical. Product analysis showed that different lycopene isomers are formed, including substantial amounts of the all-trans form, together with 7,7',9,9'-tetracis prolycopene via the corresponding neurosporene isomers. The application of different geometric isomers as substrates revealed that the ζ-carotene desaturase has no preference for certain isomers and that the nature of the isomers formed during catalysis depends strictly on the isomeric composition of the substrate.