Microsomes plant, isolation

DU, L., HALKIER, B.A., Isolation of a microsomal enzyme system involved in glucosinolate biosynthesis from seedlings of Tropaeolum majus L, Plant Physiol., 1996,111,831-837. 

Molinate has a low toxicity to rats, oral LDso=720 mg/kg, and is rapidly metabolized by plants to CO2 (1) (5) and naturally occurring plant constituents (1). Molinate is also readily metabolized by soil microorganisms (6). After incubation of molinate with Bacillus sp. 24, Nocardia sp. 119, and Micrococcus sp. 22r which were isolated from Russian garden soils and rice field drains (7,8), it was found that molinate was completely degraded into various hydroxy and oxidized products in the medium. Molinate can be metabolized to its corresponding sulfoxide in the mouse in vivo and by the microsome-NADPH system of mouse liver (9, 10). Hubbell et al. (11) and DeBaun et al. (12) also found molinate sulfoxide along with other polar and nonpolar metabolites in rat urine. 

Mohamed AA, Khalil I, Varanini Z and Pinton R (2000) Increase in NAD(P)H-dependent generation of active oxygen species and changes in lipid composition of microsomes isolated from roots of zinc-deficient bean plants. J Plant Nutr 23 285-295. 

Furthermore, an acyclic astin J (307) has been isolated (186). Cheng et al. reported this kind of acyclic peptide, the asterinins A-C, from the same plant (187). Base-catal) zed cleavage of astins A, B, and C with a fi,y-dichlorinated proline resulted in acyclic peptides with pyrrole rings, which were considered to be produced by dechlorination and aromatization from Pro(Cl2) to pyrrole imder basic conditions, following the cleavage of the amide bond in Pro. The acyclic astin B was also produced from the cyclic astin B by hepatic microsomal biotransformation in rats (Fig. 36) (188). 

H. Diesperger, C.R. Mueller, H. Sandermann, Rapid isolation of a plant microsomal fraction by Mg2+ - precipitation, FEBS Letters 43 (1974),... 

PHB of 130-170 monomer units is usually associated with other macromolecules by multiple coordinate bonds, or by hydrogen bonding and hydrophobic interactions (Reusch 1992). This conserved PHB has been isolated from the plasma membranes of bacteria, from a variety of plant tissues, and from the plasma membranes, mitochondria, and microsomes of animal cells. 

However, the flavanone naringenin (10) [but not dihydro-kaempferol (13)] is the substrate for flavone formation in snapdragons. Antirrhinum majus (Scrophulariaceae) (flavone synthase II) (Fig. 11.10). In this plant, flavones arise from dehydrogenation of flavanones and not from dehydration of dihydroflavonols (Britsch et al., 1981). A similar enzyme system converts dihydroflavonols to flavonols (Britsch et al., 1981). In other work, the enzyme responsible for oxidation of flavanones to flavones in snapdragon Antirrhinum majus) was isolated from a microsomal fraction and shown to require NADPH and molecular oxygen (Britsch et al., 1981 Dewick, 1989 Forkmann and Stotz, 1981). The system appears to be a cytochrome P-450-dependent monooxygenase. This system also is known from Glycine max... 

The enzymes responsible for the hydroxylation of monoterpenes such as (— )-limonene (11) from peppermint Mentha piperita), spearmint Mentha spicata), and perilla Per-ilia frutescens) have been isolated and characterized (Karp et al., 1987,1990). Microsomal preparations from the epidermal oil glands of these plants catalyze the NADPH and 02-dependent allylic hydroxylation of (- )-(45)-limonene (the major olefinic constituent of each of the three species) at C-3, C-6, and C-7, respectively, to produce (- )-rra j-isopiper-itenol (34), (- )- m 5-carveol (35), and (- )-perillyl alcohol (36) (Fig. 19.9) (Karp et al., 1990). These transformations are the key steps in the biosynthesis of oxygenated monoterpenes in the respective species. The enzymes appear to be... 

To determine which organelles were involved in lipid synthesis, plant cell organelles (mitochondria, microsomes, peroxisomes, plasmalemma, nuclei) were isolated in vitro and fed with various radioactive precursors ([ C]ace-tate or [ C]acetyl-CoA, [ K ]malonate or [ K ]malonyl-CoA, [ P]phos-phate, [ C]glycerol or [ K]l]glycerophosphate, [ C]choline or [ CJethanola-mine, etc.). The biosynthetic capacities of each organelle were thus evidenced (see Mazliak, 1975, 1977) in an effort to locate the sites of lipid synthesis in plant cells. The following points appeared clearly from the experiments ... 

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