title: Enzymatic synthesis of quinolizidine alkaloid esters: a tigloyl-CoA: 13-hydroxylupanine O-tigloyltransferase from Lupinus albus L.
abstract: A tigloyl-CoA: 13-hydroxylupanine O-tigloyl-transferase could be demonstrated in crude enzyme preparations from Lupinus albus seedlings. The enzyme activity increases concomitantly with for formation of 13-tigloyloxylupanine in developing lupin seedlings. The transferase catalyzes specifically the transfer of an acyl group to 13-hydroxylupanine. The apparent Km-values are 140 μM for tigloyl-CoA and 18 μM for 13-hydroxylupanine. Other hydroxylated compounds, e.g., lupinine, 4-hydroxylupanine, and cholesterol are not acylated. The transferase shows optimal activity at pH 7-8 and at 30°C. It is activated by dithioerythritol and inhibited by thiol reagents. Tigloyl-CoA can be replaced as acyl donor by benzoyl-CoA and to a lesser extent by valeroyl-CoA, 3-methylbutyryl-CoA, butyryl CoA and propionyl-CoA but not acetyl-CoA. Preliminary evidence indicates that the transfer of the tigloyl and benzoyl moieties is catalyzed by different enzymes. The transferase activity could only be demonstrated in plants which produce quinolizidine alkaloids.
authors.affiliation: Institut für Pharmazeutische Biologie der Technischen Universität, Mendelssohnstraße 1, D-3300, Braunschweig, Federal Republic of Germany.
authors.forename: M
authors.initials: M
authors.lastname: Wink
authors.forename: T
authors.initials: T
authors.lastname: Hartmann