Department of Biochemistry, Michigan State University, East Lansing, Michigan 48824.
Plant Physiol. 1992 Feb;98(2):578-83. doi: 10.1104/pp.98.2.578.
Carbonyl sulfide (COS), a substrate for carbonic anhydrase, inhibited alkalization of the medium, O(2) evolution, dissolved inorganic carbon accumulation, and photosynthetic CO(2) fixation at pH 7 or higher by five species of unicellular green algae that had been air-adapted for forming a CO(2)-concentrating process. This COS inhibition can be attributed to inhibition of external HCO(3) (-) conversion to CO(2) and OH(-) by the carbonic anhydrase component of an active CO(2) pump. At a low pH of 5 to 6, COS stimulated O(2) evolution during photosynthesis by algae with low CO(2) in the media without alkalization of the media. This is attributed to some COS hydrolysis by carbonic anhydrase to CO(2). Although COS had less effect on HCO(3) (-) accumulation at pH 9 by a HCO(3) (-) pump in Scenedesmus, COS reduced O(2) evolution probably by inhibiting internal carbonic anhydrases. Because COS is hydrolyzed to CO(2) and H(2)S, its inhibition of the CO(2) pump activity and photosynthesis is not accurate, when measured by O(2) evolution, by NaH(14)CO(3) accumulation, or by (14)CO(2) fixation.
羰基硫（COS）是碳酸酐酶的底物，可抑制五种适应空气的单细胞绿藻在 pH7 或更高时介质的碱化、O2 释放、溶解无机碳积累和光合作用 CO2 固定，这些藻形成了 CO2 浓缩过程。这种 COS 抑制作用可归因于对活性 CO2 泵中碳酸酐酶成分的外部 HCO3-（-）转化为 CO2 和 OH-（-）的抑制。在 pH5 至 6 的低 pH 值下，COS 通过没有介质碱化的低 CO2 介质刺激藻类光合作用中的 O2 释放。这归因于碳酸酐酶对 CO2 的部分 COS 水解。尽管 COS 对 Scenedesmus 中的 HCO3-（-）泵在 pH9 时的 HCO3-（-）积累的影响较小，但 COS 通过抑制内部碳酸酐酶减少了 O2 释放。因为 COS 被水解为 CO2 和 H2S，所以当通过 O2 释放、NaH（14）CO3 积累或（14）CO2 固定来测量时，其对 CO2 泵活性和光合作用的抑制作用并不准确。
