Carotene cis-trans-isomerase that converts 7,9,9'-tri-cis-neurosporene to 9'-cis-neurosporene and 7,9,9',7'-tetra-cis-lycopene (also known as prolycopene) into all-trans-lycopene. Isomerization requires redox-active components, suggesting that isomerization is achieved by a reversible redox reaction acting at specific double bonds. Isomerizes adjacent cis-double bonds at C7 and C9 pairwise into the trans-configuration, but is incapable of isomerizing single cis-double bonds at C9 and C9' (By similarity). 7,7',9,9'-tetra-cis-lycopene = all-trans-lycopene Carotenoid biosynthesis; lycopene biosynthesis. Up-regulated in the flower buds and flower lip tissue, while it is weakly expressed in leaves. Belongs to the carotenoid/retinoid oxidoreductase family. CrtISO subfamily.