Stereochemistry of allene biosythesis and the formation of the acetylenic carotenoid diadinoxanthin and peridinin (C37) from neoxanthin

Intact cells of the alga Amphidinium carterae (Dinophyceae), and a cell-free system prepared from it, incorporated 14C, 3H-labelled mevalonate into lycopene, beta, beta-carotene, zeaxanthin, neoxanthin, diadinoxanthin and peridinin. The 14C/3H ratios of zeaxanthin, neoxanthin and diadinoxanthin formed from (2RS,3R)-[2-14C,2-3H2]mevalonate show that a hydrogen atom from C-2 of mevalonate is retained in the allene at C-8, and also at C-12 of peridinin. (3R,4R + 3S,4S)-[2-14C,4-3H1]Mevalonate gave 14C/3H ratios in peridinin which show that C-14 is lost. The three carbon atoms excised during the formation of the C37 carotenoid peridinin are C-13, C-14 and C-20 of neoxanthin.