Catalytic properties of an expressed and purified higher plant typeζ‐carotene desaturase fromCapsicum annuum

Abstract
The ζ‐carotene desaturase fromCapsicum annuum(EC 1.14.99.‐) was expressed inEscherichia coli, purified and characterized biochemically. The enzyme acts as a monomer with lipophilic quinones as cofactors.Kmvalues 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‐transform, together with 7,7′,9,9′‐tetracisprolycopene 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.