Hu Q, Miyashita H, Iwasaki I, Kurano N, Miyachi S, Iwaki M, Itoh S
Marine Biotechnology Institute, Kamaishi Laboratories, Heita, Kamaishi City, Iwate 026, Japan.
Proc Natl Acad Sci U S A. 1998 Oct 27;95(22):13319-23. doi: 10.1073/pnas.95.22.13319.
A far-red type of oxygenic photosynthesis was discovered in Acaryochloris marina, a recently found marine prokaryote that produces an atypical pigment chlorophyll d (Chl d). The purified photosystem I reaction center complex of A. marina contained 180 Chl d per 1 Chl a with PsaA-F, -L, -K, and two extra polypeptides. Laser excitation induced absorption changes of reaction center Chl d that was named P740 after its peak wavelength. A midpoint oxidation reduction potential of P740 was determined to be +335 mV. P740 uses light of significantly low quantum energy (740 nm = 1.68 eV) but generates a reducing power almost equivalent to that produced by a special pair of Chl a (P700) that absorbs red light at 700 nm (1.77 eV) in photosystem I of plants and cyanobacteria. The oxygenic photosynthesis based on Chl d might either be an acclimation to the far-red light environments or an evolutionary intermediate between the red-absorbing oxygenic and the far-red absorbing anoxygenic photosynthesis that uses bacteriochlorophylls.
在滨海无叶绿素藻中发现了一种远红型的产氧光合作用，滨海无叶绿素藻是最近发现的一种海洋原核生物，它能产生一种非典型色素叶绿素d（Chl d）。滨海无叶绿素藻纯化的光系统I反应中心复合物中，每1个叶绿素a含有180个Chl d，并含有PsaA - F、- L、- K以及另外两种多肽。激光激发诱导反应中心Chl d的吸收变化，根据其峰值波长将其命名为P740。P740的中点氧化还原电位测定为 +335 mV。P740利用量子能量极低的光（740 nm = 1.68 eV），但产生的还原能力几乎与植物和蓝细菌光系统I中吸收700 nm红光（1.77 eV）的一对特殊叶绿素a（P700）所产生的还原能力相当。基于Chl d的产氧光合作用可能要么是对远红光环境的一种适应，要么是在吸收红光的产氧光合作用和利用细菌叶绿素吸收远红光的无氧光合作用之间的一种进化中间体。
