Purification and characterization of deacetylipecoside synthase from Alangium lamarckii Thw
1998
Nitima Suttipanta | Wanchai De-Eknamkul (Chulalongkorn Univ., Bangkok (Thailand). Faculty of Pharmaceutical Sciences)
Deacetylipecoside synthase, the enzyme condensing dopamine and secologanine to form the (R)-epimer of deacetylipecoside, has been purified from the leaves of Alangium lamarckii to apparent electrophoretic homogeneity by ammonium sulphate precipitation and three subsequent column chromatography steps. The isolates enzyme is a single polypeptide with Mr 30 000 and has a pH optimum at 7.5 and a temperature optimum at 40 deg C. The apparent Km values for dopamine and secologanin are 0.7 and 0.9 mM, respectively. The enzyme exhibits high substrate specificity toward dopamine; neither tyramine nor tryptamine are utilized by the enzyme. The enzyme activity is not inhibited by its substrate of dopamine but inhibited by alangimakrine and dehydroalangimakrine with similar I50 value of 10 mM. Deacetylipecoside synthase catalyzes the provision of (R)-deacetylipecoside for the formation of tetrahydroisoquinoline monoterpene glucosides that possess also (R)-configuration at the same chiral center.
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