Porra R J, Schäfer W, Katheder I, Scheer H
Botanisches Institut der Universität München, Germany.
FEBS Lett. 1995 Aug 28;371(1):21-4. doi: 10.1016/0014-5793(95)00854-3.
Using mass spectrometry, we have demonstrated 18O-labelling of both the 13(1)-oxo and 3-acetyl groups of newly-formed bacteriochlorophyll a synthesized by Rhodobacter sphaeroides cells during adaptation from respiratory to photosynthetic conditions in the presence of H218O. This derivation of the 13(1)-oxo group of bacteriochlorophyll a from water provides a stark contrast with that of chlorophylls in higher plants where ring E formation is an aerobic process in which the 13(1)-oxo group arises from molecular oxygen via an oxygenase activity. The formation of the 3-acetyl group of bacteriochlorophyll a, however, is consistent with the enzymic hydration of the 3-vinyl group of a derivative of chlorophyll a.
利用质谱分析法，我们已经证明，在存在H218O的情况下，球形红细菌细胞从呼吸状态适应光合状态的过程中，新合成的细菌叶绿素a的13(1)-氧代基团和3-乙酰基均被18O标记。细菌叶绿素a的13(1)-氧代基团来源于水，这与高等植物叶绿素形成了鲜明对比，在高等植物中，E环的形成是一个需氧过程，其中13(1)-氧代基团通过加氧酶活性来源于分子氧。然而，细菌叶绿素a的3-乙酰基的形成与叶绿素a衍生物的3-乙烯基的酶促水合作用是一致的。
