[Metabolism of nicotinic acid in plant cell suspension cultures: II; Isolation, characterization and enzymology of nicotinic acid N-alpha-arabinoside (author's transl)].

A very hydrophilic compound was isolated from parsley cell suspension cultures in high yield after application of nicotinic acid. Using chemical, chromatographic and spectroscopic procedures the structure of this new plant constituent has been elucidated as nicotinic acid N-alpha-L-arabinopyranoside. This structure has been proved by chemical synthesis. An arabinosyltransferase was isolated from parsley cell suspension cultures and purified about 19-fold. The enzyme converted nicotinic acid N-alpha-arabinoside with UDP to nicotinic acid and UDP-arabinose. pH-Optimum (pH 7.0-8.0), Km value for nicotinic acid N-alpha-L-arabinoside (2.2 X 10(-4) mol/l) and mol. wt. (app. 70 000) of the transferase were measured. Function and biosynthesis of the arabinoside in cell cultures are discussed.