Plants microsomes

Benveniste, I., Gabriac, B., and Durst, F., Purification and characterization of the NADPH-cytochrome P-450 (cytochrome c) reductase from higher-plant microsomal fraction, Biochem. J., 235, 365-373, 1986. 

Salaun, J.P., Benveniste, I., Reichhart, D., and Durst, F., Induction and specificity of a (cytochrome P-450-dependent) laurate in-chain-hydroxylase from higher plant microsomes, Eur. J. Biochem., 119, 651-655, 1981. 

Salaun, J.P., Weissbart, D., Durst, F., Pflieger, P., and Mioskowski, C., Epoxidation of cis and trans 9-unsaturated lauric acids by a cytochrome P-450-dependent system from higher plant microsomes, FEBS Lett., 246, 120-126, 1989. 

Stahl, U., Banas, A., and Stymne, S. 1995. Plant microsomal phospholipid acyl hydrolases have selectivities for uncommon fatty acids. Plant Physiol., 107, 953-962. 

Grand, C. (1984) Ferulic acid 5-hydroxylase a new cytochrome P4so-dependent enzyme from higher plant microsomes involved in lignin synthesis. FEBS Lett., 169, 7-11. 

Pascal, S., Taton, M. and Rahier, A. (1990) Oxidative C4-demethylation of 24-methylene cycloartanol by a cyanide-sensitive enzymatic system from higher plant microsomes. Biochem. Biophys. Res. Commun., 172,98-106. 

Plant microsomes contains another cytochrome which is very similar to mammalian cytochrome 65 (157,275,281-284). The absorption peaks, molecular weight, and Ea at pH 7 of cytochrome 6-555 purified frommung bean seedlings (157) are given in Table V. The a band of this cytochrome is split into two peaks at liquid nitrogen temperature in a way similar to mammalian cytochrome 63 (145). 

GRAND, C., Ferulic Acid 5-Hydroxylase - a New Cytochrome P-450-Dependent Enzyme from Higher-Plant Microsomes Involved in Lignin Synthesis, FEBS Lett., 1984,169, 7-11. 

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

Secondly, one wants a structure which is a good acceptor for an acyl group but a poor one for a phosphoryl group. This could be an SH, a reactive OH, or the NH of an imidazole or amide group. Among the known vitamins and cofactors there are, of course, several with the necessary structural requirements outlined above. The first to come to mind is CoA, but so far it has not been possible to demonstrate a CoA requirement for amino acid incorporation into mammalian or plant microsomes. Nevertheless this vitamin seems to be essential for the incorporation of amino acids into the proteins of hen oviducts (56) and it does, of course, the job of displacing activated fatty acids from their activating enzymes (170). Vitamin Bi2 also fits the structural requirements and it has, indeed, been claimed to be essential for amino acid activation and subsequent incorporation into rat liver microsomes (i07, 178, 179), but this requirement has not yet been confirmed by other authors (180,181). 

Sperling P Heinz E. Isomeric sn-l-octadecenyl and sn-2-octadecenyl analogues of lysophosphatidylcholine as substrates for acylation and desaturation by plant microsomal membranes. Eur J Biochem 1993 213 965-971. 

In plants, the polyunsaturated fatty acids linoleate (octadeca-A9,12-dienoic acid) and a-linolenate (octadeca-A6,9,15-trienoic acid) are synthetized by A12- and A15-desaturases, respectively. They are essential fatty acid components of human nutrition as precursors of prostaglandins. Plant A12-desaturase (oleic acid - linoleic acid) is a well known membrane-bound enzyme present in endoplasmic reticulum of developing seeds. A12-desaturase employs NADH and molecular oxygen and requires cytochrome b5 and NADH-cytochrome b5 reductase as intermediate electron carrier (Demandre etaLy 1986). In contrast, in vitro A15-desaturase activity (linoleic acid — a-linolenic acid) is actually not observed in plant microsomes. 

While progress is being made in this area of plant metabolism, difficulties associated with the isolation of plant microsomal preparations active in the utilization of other herbicide substrates, and with the purification of the active mfo enzymes themselves, are still to be resolved. Consequently, only slow progress has been made on the identification of specific mfo polypeptides suitable as candiates for gene transfer studies. Such studies are aimed at manipulating crop plants for herbicide resistance based on enhanced oxidative detoxification. 

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