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  • 1
    Electronic Resource
    Electronic Resource
    Levels of tropinone-reductase activities influence the spectrum of tropane esters found in transformed root cultures of Datura stramonium L. (1992)
    Springer
    Planta 188 (1992), S. 581-586 
    Details
    ISSN: 1432-2048
    Keywords: Datura (root, alkaloid) ; Enzyme inhibition ; Root culture (alkaloid production) ; 8-Thiabicyclo[3.2.1]octan-3-one ; 8-Thiabicyclo[3.2.1]octan-3-ol ; Tropane alkaloid biosynthesis ; Tropinone reductase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The nortropane sulphur analogues 8-thiabicyclo[3.2.1] octan-3-one, 8-thiabicyclo[3.2.1]octan-3a-ol and 8-thiabicyclo[3.2.1]octan-3β-ol have been found to have differential effects in vitro on the activities of tropinone reductase I and tropinone reductase II from Datura stramonium L. It has been demonstrated that only tropinone reductase I is able to metabolise 8-thiabicyclo[3.2.1]octan-3-one and that only this enzyme is inhibited by 8-thiabicyclo[3.2.1]octan-3α-ol and 8-thiabicyclo[3.2.1]octan-3β-ol. A K m of 0.035 mM was determined for 8-thiabicyclo[3.2.1]octan-3-one and I50 values of 0.081 mM and 0.021 mM for 8-thiabicyclo[3.2.1]octan-3α-ol and 8-thiabicyclo[3.2.1]octan-3β-ol, respectively. The influence that these differential interactions might have on metabolism was investigated in transformed root cultures of D. stramonium. It was found that when these cultures were grown in the presence of either 8-thiabicyclo[3.2.1]octan-3-one or 8-thiabicyclo[3.2.1]octan-3β-ol the spectrum of alkaloids that accumulated was altered from that found in control roots in the manner predicted from the observed effects of these inhibitors on the isolated reductases. The effect could be mimicked by feeding pseudotropine, the product of tropinone reductase II. It is concluded that the relative levels of activity of the two tropinone reductases might play an important role in regulating the balance of tropan-3α-ols to tropan-3β-ols seen in the spectrum of tropane-alkaloid-producing plants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00197052
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  • 2
    Electronic Resource
    Electronic Resource
    Purification and properties of putrescine N-methyltransferase from transformed roots of Datura stramonium L. (1994)
    Springer
    Planta 193 (1994), S. 9-15 
    Details
    ISSN: 1432-2048
    Keywords: Datura ; Cadaverine ; Putrescine-N-methyltransferase ; Root culture (Agrobacterium-transformed) ; Tropane alkaloid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Putrescine-N-methyltransferase (PMT; EC 2.1.1.53), the first enzyme in the biosynthetic pathway leading from putrescine to tropane and pyrrolidine alkaloids, has been purified about 700-fold from root cultures of Datura stramonium established following genetic transformation with Agrabacterium rhizogenes. The native enzyme had a molecular weight estimated by gel-permeation chromatography on Superose-6 of 40 kDa; sodium dodecyl sulphate-polyacrylamide gel electrophoresis of the peak fractions from Superose-6 chromatography revealed a band of 36 kDa molecular weight. Kinetic studies of the purified enzyme gave K m values for putrescine and S-adenosyl-l-methionine of 0.31 mM and 0.10 mM, respectively, and K i values for S-adenosyl-l-homocysteine and N-methylputrescine of 0.01 mM and 0.15 mM, respectively. The enzyme was active with some derivatives and analogous of putrescine, including 1,4-diamino-2-hydroxybutane and 1,4-diamino-trans-but-2-ene. Little activity was observed with 1,4-diamino-cis-but-2-ene and none with 1,3-diaminopropane or 1,5-diaminopentane (cadaverine), indicating a requirement for substrate activity of two amino groups in a trans conformation, separated by four carbon atoms. A large number of monoamines were inhibitors of the enzyme. Though not a substrate, cadaverine was a competitive inhibitor of the enzyme, with a K i of 0.04 mM; the significance of this in relation to the biosynthesis of cadaverine-derived alkaloids is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00191600
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  • 3
    Electronic Resource
    Electronic Resource
    Enzymes of N-methylputrescine biosynthesis in relation to hyoscyamine formation in transformed root cultures of Datura stramonium and Atropa belladonna (1990)
    Springer
    Planta 182 (1990), S. 136-141 
    Details
    ISSN: 1432-2048
    Keywords: Atropa ; Datura ; Hyoscyamine ; N-Methyl-putrescine ; Tropane alkaloids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The activities of enzymes related to the biosynthesis of N-methylputrescine, a precursor of the alkaloid hyoscyamine, have been measured in root cultures of Datura stramonium L. and Atropa belladonna L. transformed with Agrobacterium rhizogenes. Ornithine δ-Nmethyltransferase and δ-N-methylornithine decafboxylase were undetectable, indicating that δ-N-methylornithine is an unlikely intermediate in the formation of N-methylputrescine. The activity of putrescine-N-methyltransferase (EC 2.1.1.53) was comparable to, or greater than, that of arginine decarboxylase (EC 4.1.1.19) or ornithine decarboxylase (EC 4.1.1.17). Radiolabel from dl-[5-14C]ornithine, l-[U-14C]arginine, [U-14C]agmaine and [1,4-14C]putrescine was incorporated into hyosyamine by Datura cultures. Hyoscyamine production by Datura cultures was substantially inhibited by the arginine-decarboxylase inhibitor, dl-α-difluoromethylarginine, but not by the corresponding ornithine-decarboxylase inhibitor, dl-α-difluoromethylornithine. Together with the demonstration that label was incorporated from [U-14C]agmatine, this indicates clearly that arginine is metabolised to hyoscyamine at least in part via decarboxylation to agmatine, even though a high activity of arginase (EC 3.5.3.1) was measurable under optimal conditions. The effect of unlabelled putrescine in diminishing the incorporation into hyoscyamine of label from dl-[ 5-14C] ornithine and l-[U-14C] arginine does not lend support to the theory that ornithine is metabolised via a bound, asymmetric putrescine intermediate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00239995
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  • 4
    Electronic Resource
    Electronic Resource
    Esterification reactions in the biosynthesis of tropane alkaloids in transformed root cultures (1994)
    Springer
    Plant cell, tissue and organ culture 38 (1994), S. 241-247 
    Details
    ISSN: 1573-5044
    Keywords: Acryl-coenzyme A transferase ; biosynthesis ; coenzyme A thioester ; Datura ; pseudotropine ; transformed root cultures ; tropane alkaloids ; tropine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Transformed root cultures of Datura stramonium and of related species contain both aliphatic and aromatic tropane esters. It has been shown that these esters are produced by the action of several acyl transferases that transfer the acidic moiety to tropan-3α-ol (tropine) or tropan-3β-ol (pseudotropine) from various acyl-coenzyme A thioesters. The presence of these enzymes has been examined in a range of tropane-alkaloid-producing and non-tropane-alkaloid-producing species. Activities that esterify tropine appear to be confined to species that accumulate tropane alkaloids, whereas a number of species that do not accumulate tropane alkaloids possess some ability to esterify pseudotropine. The present state of knowledge of these enzymes is reviewed. One of these activities, tigloyl-Coenzyme A:pseudotropine acyl transferase, has been purified to near homogeneity and the properties of this enzyme are summarized.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00033883
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