Rees J F, de Wergifosse B, Noiset O, Dubuisson M, Janssens B, Thompson E M
Laboratory of Animal Physiology, Catholic University of Louvain, Louvain-la-Neuve, Belgium.
J Exp Biol. 1998 Apr;201(Pt 8):1211-21. doi: 10.1242/jeb.201.8.1211.
Bioluminescence, the emission of ecologically functional light by living organisms, emerged independently on several occasions, yet the evolutionary origins of most bioluminescent systems remain obscure. We propose that the luminescent substrates of the luminous reactions (luciferins) are the evolutionary core of most systems, while luciferases, the enzymes catalysing the photogenic oxidation of the luciferin, serve to optimise the expression of the endogenous chemiluminescent properties of the luciferin. Coelenterazine, a luciferin occurring in many marine bioluminescent groups, has strong antioxidative properties as it is highly reactive with reactive oxygen species such as the superoxide anion or peroxides. We suggest that the primary function of coelenterazine was originally the detoxification of the deleterious oxygen derivatives. The functional shift from its antioxidative to its light-emitting function might have occurred when the strength of selection for antioxidative defence mechanisms decreased. This might have been made possible when marine organisms began colonising deeper layers of the oceans, where exposure to oxidative stress is considerably reduced because of reduced light irradiance and lower oxygen levels. A reduction in metabolic activity with increasing depth would also have decreased the endogenous production of reactive oxygen species. Therefore, in these organisms, mechanisms for harnessing the chemiluminescence of coelenterazine in specialised organs could have developed, while the beneficial antioxidative properties were maintained in other tissues. The full range of graded irradiance in the mesopelagic zone, where the majority of organisms are bioluminescent, would have provided a continuum for the selection and improvement of proto-bioluminescence. Although the requirement for oxygen or reactive oxygen species observed in bioluminescent systems reflects the high energy required to produce visible light, it may suggest that oxygen-detoxifying mechanisms provided excellent foundations for the emergence of many bioluminescent systems.
生物发光是生物体发出具有生态功能的光，它在多个场合独立出现，但大多数生物发光系统的进化起源仍不清楚。我们提出，发光反应的发光底物（荧光素）是大多数系统的进化核心，而催化荧光素光致氧化的酶——荧光素酶，则用于优化荧光素内源性化学发光特性的表达。腔肠素是一种存在于许多海洋生物发光群体中的荧光素，具有很强的抗氧化特性，因为它与超氧阴离子或过氧化物等活性氧高度反应。我们认为，腔肠素的主要功能最初是对有害氧衍生物进行解毒。当对抗氧化防御机制的选择强度降低时，其功能可能从抗氧化转变为发光。当海洋生物开始在海洋更深层定居时，这种转变可能成为可能，因为在更深层，由于光照强度降低和氧气水平降低，暴露于氧化应激的程度大大降低。随着深度增加，代谢活动的减少也会降低活性氧的内源性产生。因此，在这些生物中，利用腔肠素在专门器官中进行化学发光的机制可能已经发展起来，而有益的抗氧化特性则在其他组织中得以保留。在大多数生物会发光的中层带，全范围的分级辐照度为原生物发光的选择和改进提供了一个连续体。虽然在生物发光系统中观察到的对氧气或活性氧的需求反映了产生可见光所需的高能量，但这可能表明氧气解毒机制为许多生物发光系统的出现提供了良好的基础。
