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

The zeta-carotene desaturase from Capsicum annuum (EC 1.14.99.-) was expres sed in Escherichia coli, purified and characterized biochemically. The enzy me acts as a monomer with lipophilic quinones as cofactors. K-m values for the substrate zeta-carotene or the intermediate neurosporene in the two-ste p desaturation reaction ore 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 corre sponding neurosporene isomers. The application of different geometric isome rs as substrates revealed that the zeta-carotene desaturase has no preferen ce for certain isomers and that the nature of the isomers formed during cat alysis depends strictly on the isomeric composition of the substrate.