chlorophyllide-b and chlorophyllide-a

Chlorophyllides can be found in photosynthetic organisms. Generally, chlorophyllides have

Topics: Anti-Infective Agents; Antineoplastic Agents, Phytogenic; Antiviral Agents; Biosensing Techniques; Chemistry, Pharmaceutical; Chlorophyll; Chlorophyllides; Electrochemical Techniques; Food Additives; Humans; Light; Molecular Structure; Photosynthesis; Plants; Protochlorophyllide

The inhibitory effects of four chlorophyll derivatives (chlorophyllide [Chlide] a and b and pheophorbide [Pho] a and b) on aflatoxin B1 (AFB1)-DNA adduct formation, and on the modulation of hepatic glutathione S-transferase (GST) were evaluated in murine hepatoma (Hepa-1) cells. Enzyme-linked immunosorbent assay showed that pretreatment with Chlide or Pho significantly reduced the formation of AFB1-DNA adducts, and that Pho was the most potent inhibitor. However, wash-out prior to adding AFB1 totally eliminated inhibition by Childe and partially eliminated inhibition by Pho, indicating that the inhibitory effect of Chlide, and to some extent Pho, was mediated through direct trapping of AFB1. Furthermore, spectrophotometric analysis showed that Pho treatment could increase GST activity in Hepa-1 cells. These observations indicate that the chlorophyll derivatives studied may attenuate AFB1-induced DNA damage in the Hepa-1 cell by direct trapping of AFB1. Pho provided additional protection not only by direct trapping, but also by increasing GST activity against hepatic AFB1 metabolites.

Topics: Aflatoxin B1; Animals; Anticarcinogenic Agents; Cell Line, Tumor; Chlorophyll; Chlorophyllides; DNA Adducts; Glutathione Transferase; Liver Neoplasms, Experimental; Mice

In angiosperm plants, the etioplast-chloroplast transition is light-dependent. A key factor in this process is the protochlorophyllide oxidoreductase A (PORA), which catalyzes the light-induced reduction of protochlorophyllide to chlorophyllide. The import pathway of the precursor protein prePORA into chloroplasts was analyzed in vivo and in vitro by using homozygous loss-of-function mutants in genes coding for chlorophyllide a oxygenase (CAO) or for members of the outer-envelope solute-channel protein family of 16 kDa (OEP16), both of which have been implied to be key factors for the import of prePORA. Our in vivo analyses show that cao or oep16 mutants contain a normally structured prolamellar body that contains the protochlorophyllide holochrome. Furthermore, etioplasts from cao and oep16 mutants contain PORA protein as found by mass spectrometry. Our data demonstrate that both CAO and OEP16 are dispensable for chloroplast biogenesis and play no central role in the import of prePORA in vivo and in vitro as further indicated by protein import studies.

Topics: Arabidopsis; Arabidopsis Proteins; Base Sequence; Chlorophyllides; Chloroplasts; DNA Primers; Genes, Plant; Ion Channels; Mutation; Oxygenases; Photobiology; Protein Transport; Protochlorophyllide

The Arabidopsis CAO gene encodes a 52-kDa protein with predicted localization in the plastid compartment. Here, we report that CAO is an intrinsic Rieske iron-sulfur protein of the plastid-envelope inner and thylakoid membranes. Activity measurements revealed that CAO catalyzes chlorophyllide a to chlorophyllide b conversion in vitro and that the enzyme was only slightly active with protochlorophyllide a, the nonreduced precursor of chlorophyllide a. Protein import and organelle fractionation studies identified CAO to be distinct from Ptc52 in the substrate-dependent transport pathway of NADPH:protochlorophyllide oxidoreductase A but instead to be part of a separate translocon complex. This complex was involved in the regulated import and stabilization of the chlorophyllide b-binding light-harvesting proteins Lhcb1 (LHCII) and Lhcb4 (CP29) in chloroplasts. Together, our results provide insights into the plastid subcompartmentalization and evolution of chlorophyll precursor biosynthesis in relation to protein import in higher plants.

Topics: Arabidopsis; Chlorophyllides; Electron Transport Complex III; Enzyme Stability; Iron-Sulfur Proteins; Light-Harvesting Protein Complexes; Oxygenases; Photosystem II Protein Complex; Protein Kinases; Protein Transport; Thylakoids

Chlorophylls (Chl's) are the most abundant natural plant pigments. Four chlorophyll-related compounds (CRCs), including chlorophyllide a and b (Chlide a and b) and pheophorbide a and b (Pho a and b), were investigated for their antioxidative capacities to protect human lymphocyte DNA from hydrogen peroxide (H(2)O(2)) induced strand breaks and oxidative damage ex vivo. Lymphocytes exposed to H(2)O(2) at concentrations of 10 and 50 microM revealed an increased frequency of DNA single-strand breaks (ssb's; as measured by the comet assay) and also an increased level of oxidized nucleoside (as measured by 8-hydroxydeoxyguanosine, 8-OHdG). All Chl's reduced the level of DNA ssb's and 8-OHdG within human lymphocytes following exposure to 10 microM H(2)O(2). Only Pho a and b were able to decrease DNA ssb's and 8-OHdG following treatment of lymphocytes with 50 microM H(2)O(2), in a concentration-dependent fashion. It was demonstrated herein that Pho a and b were more antioxidative than others. We applied DPPH free-radical scavenge assays in vitro, and got similar results. Pho a and b had higher ability in scavenging capacities than others. We conclude that water-extract Chl's are able to enhance the ability of human lymphocytes to resist H(2)O(2)-induced oxidative damage, especially for Pho a and b.

Topics: Antioxidants; Chlorophyll; Chlorophyllides; DNA Damage; Humans; Hydrogen Peroxide; Lymphocytes