Biosynthesis subcellular localization

The estrogens are a family of hormones synthesized in a variety of tissues. 17P-Estradiol is the primary estrogen of ovarian origin. In some species, estrone, synthesized in numerous tissues, is more abundant. In pregnancy, relatively more estriol is produced, and this comes from the placenta. The general pathway and the subcellular localization of the enzymes involved in the early steps of estradiol synthesis are the same as those involved in androgen biosynthesis. Features unique to the ovary are illustrated in Figure 42-7. 

Suzuki, H., Koike, Y., Murakoshi, I. and Saito, K. 1996. Subcellular local ization of acyltransferases for quinolizidine alkaloid biosynthesis in Lupinus. Phytochemistry, 42 1557-1562. 

Hrazdina G, Wagner GJ, Siegelman HW. 1978. Subcellular localization of enzymes of anthocyanin biosynthesis in protoplasts. Phytochem 17 53-56. 

DE LUCA, V., CUTLER, A.J., Subcellular localization of enzymes involved in indole alkaloid biosynthesis in Catharanthus roseus. Plant Physiol., 1987, 85, 1099-1102. 

KOLOSOVA, N., SHERMAN, D., KARLSON, D DUDAREVA, N., Cellular and subcellular localization of S-adenosyl-L-methionine benzoic acid carboxyl methyltransferase, the enzyme responsible for biosynthesis of the volatile ester methylbenzoate in snapdragon flowers. Plant Phys. 2001,125, 1-9. 

As part of our studies on pharmaceutically important alkaloids in C. roseus and Cinchona spp. several aspects of their bios5mthesis were chciracterized and a number of enzymes were purified [4]. In the accumulation of alkaloids in suspension cultured C. roseus cells, it was found that the supply of isoprenoid precursors was a limiting factor. This prompted us to fiarther studies, thereby focusing on the early steps of the isoprenoid biosynthesis (fig. 2). Little was known of these enzymes from plants and except for HMG-CoA reductase, none of the enzymes was characterized [5,6]. Furthermore, there exists much controversy on the subcellular localization of this pathway [7,8]. 

Glutathione is widely distributed in plants, and is commonly not only the major free sulfur amino acid but also the major free thiol compound. Relatively little attention has been devoted to the biosynthesis of glutathione in plants, or to the subcellular localization and control of this process (Sections IV,A, B, and C). By contrast, the question of the physiological role or roles for glutathione has attracted considerable interest. Discussed briefly below (Section IV,D) are several possible physiological roles for which some experimental evidence has been adduced, and which illustrate the main biochemical reactions in which this amino acid is known to participate in plants. It should be clear that at present none of these roles can be regarded as definitively established. 

The enzymes involved in the late steps of protoberberine biosynthesis, beginning with the berberine bridge enzyme all have a high pH-optimum of 8.9. This fact led to an investigation of the subcellular localization of these enzymes. After... 

Methods to study the biosynthesis of RNA in living cells, their intracellular transport, subcellular localization, and degradation are of great interest for understanding cellular networks and their malfunction [1-3] during diseases. Here, we describe the live cell RNA imaging with peptide nucleic acid-based FIT forced intercalation probes that enabled a simultaneous localization of two viral messenger ribonucleic acid (mRNA) molecules. 

The localization of enzymes of the oxylipin pathway has yet to be unequivocally elucidated. Nonetheless, LOX has been localized in plastids, vacuoles and the cytoplasm, e.g. [1], and in lipid bodies [36,37]. Since enzymes of the jasmonic acid biosynthetic pathway are thought to be localized mainly in plastids, mechanisms must exist to shuttle fatty acids released from the plasma membrane to the plastids. Furthermore, since p-oxidation of fatty acids normally occurs in peroxisomes, transport vesicles that carry the cargo between organelles may exist in plant cells. It is tempting to speculate that there could be fusion or mixing of compartments that contain either enzymes, fatty acids, and/or intermediate products, thus resulting in oxylipin biosynthesis. Intensive research is needed to address these questions as well as the cell-specific and the subcellular localization of oxylipin synthesis and the mechanisms that regulate this process. 

Fig. 95.1 Terpene biosynthesis pathways and their subcellular localization in the plants. Different classes of terpenes are respectively formed in the cytosol or the plastid by two independent pathways in the plants, that is, acetate-mevalonate pathway (MEV) (cytosol) and methylerythritol 4-phosphate (MEP) or deoxyxylulose 5-phosphate pathway (DXP) (plastid). Mraioterpcmes, diterpenes, and tetraterpenes are derived from IPP and DMAPP Irran the plastidial MEP ot DXP pathway. Sesquiterpenes and triterpenes are biosynthesized from IPP and DMAPP from the cytosol pathway. Black square with a white question mark suggests a possible transport of IPP (isopentenylpyrophosphate) from the plastid to the cytosol. Other metabolites involved in the different steps are DMAPP dimethylallylpyrophosphate, FPP famesylpyrophosphate, GASP D- glyceraldehyde- 3-phosphate, GPP geranylpyrophosphate, GGPP geranylgeranylpyro-phosphate. TPSs in the circle correspond to terpene synthases. Broken arrows show several enzymatic steps (Adapted from Aharoni et al. [8] and Sallaud et al. [154])...

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