McDermott J C, Brown D J, Britton G, Goodwin T W
Biochem J. 1974 Nov;144(2):231-43. doi: 10.1042/bj1440231.
In Flavobacterium R1519, nicotine blocks zeaxanthin biosynthesis by specifically inhibiting the cyclization reaction. Lycopene (at high nicotine concentrations, e.g. 7.5mm) and rubixanthin (at low nicotine concentration, e.g. 1mm) replace zeaxanthin as the main carotenoid. On removal of the nicotine lycopene is converted into beta-carotene under anaerobic conditions and into zeaxanthin in the presence of O(2). The conversion in vivo of beta-carotene into zeaxanthin was also demonstrated. Cyclization (an anaerobic process) thus precedes hydroxylation (O(2)-requiring) in the biosynthesis of zeaxanthin. The conversion in vivo of rubixanthin into beta-cryptoxanthin and into zeaxanthin was demonstrated, thus indicating the operation of alternative pathways of zeaxanthin biosynthesis. Several alternative biosynthetic pathways are considered and the results are also discussed in terms of reaction sequences of carotenoid ;half-molecules'.
在黄杆菌R1519中，尼古丁通过特异性抑制环化反应来阻断玉米黄质的生物合成。番茄红素（在高尼古丁浓度下，如7.5mM）和玉红黄质（在低尼古丁浓度下，如1mM）取代玉米黄质成为主要类胡萝卜素。去除尼古丁后，番茄红素在厌氧条件下转化为β-胡萝卜素，在有O₂存在时转化为玉米黄质。还证明了β-胡萝卜素在体内可转化为玉米黄质。因此，在玉米黄质的生物合成中，环化（一个厌氧过程）先于羟基化（需要O₂）。证明了玉红黄质在体内可转化为β-隐黄质和玉米黄质，从而表明存在玉米黄质生物合成的替代途径。文中考虑了几种替代生物合成途径，并根据类胡萝卜素“半分子”的反应序列对结果进行了讨论。
