Palmer J D
Department of Biology, Indiana University, Bloomington 47405, USA.
Bioessays. 1995 Dec;17(12):1005-8. doi: 10.1002/bies.950171202.
The most common form of the CO2-fixing enzyme rubisco is a form I enzyme, heretofore found universally in oxygenic phototrophs (cyanobacteria and plastids) and widely in proteobacteria. Two groups, however (1-4), now report that in dinoflagellate plastids the usual form I rubisco has been replaced by the distantly related form II enzyme, known previously only from anaerobic proteobacteria. This raises the important question of how such an oxygen-sensitive rubisco could function in an aerobic organism. Moreover, the dinoflagellate rubisco has unusual molecular properties: it is encoded as a polyprotein, by nuclear (rather than plastid) genes, and these genes contain noncanonical spliceosomal introns. The nuclear location and alpha-proteobacterial affinity of dinoflagellate rubisco genes hint at a possible mitochondrial origin and highlight the extraordinary richness of lateral gene transfers, both between and within organisms, that have occurred during rubisco evolution.
二氧化碳固定酶核酮糖-1,5-二磷酸羧化酶/加氧酶（rubisco）最常见的形式是I型酶，此前在产氧光合生物（蓝细菌和质体）中普遍存在，在变形菌门中也广泛存在。然而，有两个研究小组（1 - 4）现在报告称，在甲藻质体中，常见的I型rubisco已被远亲的II型酶取代，II型酶以前仅在厌氧变形菌中发现过。这就引出了一个重要问题：这样一种对氧敏感的rubisco如何能在需氧生物中发挥作用。此外，甲藻rubisco具有不同寻常的分子特性：它被编码为一种多蛋白，由核基因（而非质体基因）编码，并且这些基因含有非经典的剪接体内含子。甲藻rubisco基因的核定位和α-变形菌亲缘关系暗示了其可能的线粒体起源，并突出了在rubisco进化过程中生物间和生物内发生的横向基因转移的异常丰富性。
