A novel O-tigloyltransferase for alkaloid biosynthesis in plants. Purification, characterization, and distribution in Lupinus plants.
A novel acyltransferase for alkaloid metabolism, tigloyl-CoA: (-)-13 alpha-hydroxymultiflorine/(+)-13 alpha-hydroxylupanine O-tigloyltransferase (HMT/HLTase), a monomeric 50-kDa protein, was purified to homogeneity from 10-day-old Lupinus termis seedlings. There were two isoforms of this acyltransferase with the same molecular mass (50 kDa) but slightly different isoelectric points (pI 7.8 and 7.6). These two isoforms showed the same catalytic activity of tigloyl transfer from tigloyl-CoA to (-)-13 alpha-hydroxymultiflorine and (+)-13 alpha-hydroxylupanine, which belong to the same (7S, 9S) enantiomeric series of tetracyclic quinolizidine alkaloids; whereas no activity was detected toward an antipodal (7R, 9R) alkaloid, (-)-baptifoline, or to bicyclic quinolizidine alkaloids, (+)-epilupinine and (-)-lupinine. The Km values for HMTase activity were determined to be 21 microM and 46 microM for (-)-13 alpha-hydroxymultiflorine and tigloyl-CoA, respectively; and for HLTase activity, 27 microM and 52 microM for (+)-13 alpha-hydroxylupanine and tigloyl-CoA, respectively. The activity was inhibited by CoASH in a competitive manner, and by (+)-lupanine and (+)-epilupinine in a partially noncompetitive manner. The enzyme showed the highest activity around pH 8.0 and was inactivated by heat treatment and by the addition of sulfhydryl blocking reagents. Such tigloyltransferases for quinolizidine alkaloid metabolism are distributed in some Lupinus species and Cytisus scoparius, in which tigloyl alkaloids are accumulated in addition to non-ester-type alkaloids, but not in other lupin plants, in which only non-ester-type alkaloids are present.
Suzuki
H
H
Faculty of Pharmaceutical Sciences, Chiba University, Japan.
Murakoshi
I
I
Saito
K
K
D000217:Acyltransferases / Q000302:isolation & purification* / Q000378:metabolism*; D000470:Alkaloids / Q000378:metabolism*; D002845:Chromatography; D002850:Chromatography, Gel; D002852:Chromatography, Ion Exchange; D017886:Durapatite; D004591:Electrophoresis, Polyacrylamide Gel; D007887:Fabaceae / Q000201:enzymology*; D007700:Kinetics; D008970:Molecular Weight; D010946:Plants, Medicinal; D013045:Species Specificity; D013379:Substrate Specificity
D000470:Alkaloids; D017886:Durapatite; D000217:Acyltransferases; C087441:tigloyl-CoA-13-hydroxymultiflorine-13-hydroxyupanine O-tigloyltransferase