| Abstrakt: |
The 17-propionate ester group of chlorophyll(Chl)-ain some oxygenic phototrophs was investigated using HPLC. Chls-aesterified with partially dehydrogenated forms of a phytyl group were found in fully grown cells of a diatom, Chaetoceros calcitrans: geranylgeranyl (GG), dihydrogeranylgeranyl (DHGG), and tetrahydrogeranylgeranyl (THGG). Chls-abearing such esterifying groups were reported to be found only in greening processes of higher plants, and thus these Chls-ahave been thought to be biosynthetic precursors for phytylated Chl-a. Their molecular structures were unambiguously determined using 1H and 13C NMR spectroscopy and mass spectrometry. In particular, the positions of CC double bonds in DHGG were identified at C2C3, C6C7, and C14C15, and those in THGG were determined to be at C2C3 and C14C15. Notably, the present DHGG was different from the previously determined DHGG of bacteriochlorophyll-ain purple bacteria (C2C3, C10C11, and C14C15). Moreover, thylakoid membranes as well as fucoxanthin-chlorophyll-a/cproteins called FCPs were isolated from the diatom, and their Chl-acompositions were analyzed. Chls-aesterified with GG, DHGG, and THGG were detected by HPLC, indicating that such Chls-awere not merely biosynthetic precursors, but photosynthetically active pigments. |
