Characterization of Coptis japonica cells with different alkaloid productivities

Several cell lines of Coptis japonica with different alkaloid productivities were characterized to obtain information on how a high metabolite production is established. High and low metabolite producing cells, except those from one cell line, showed similar growth kinetics and a similar pattern of nutrient uptake. Amino acid contents, especially that of tyrosine, differed between cell lines, but no correlation was found between the amino acid or tyrosine levels and alkaloid production. Since the addition of tyrosine did not increase the production of berberine, this primary substrate is apparently not the limiting factor for high production in cultured Coptis cells. The addition of berberine to the medium revealed that low-producing cells also have the ability to store alkaloid, and that low productivity is not due to decomposition of alkaloids which have been produced. The direct measurement of the biosynthesis of berberine using ¹⁴C-tyrosine clearly showed that high-producing cells had a higher biosynthetic activity of berberine from tyrosine than low-producing cells. The measurement of enzyme activities in berberine biosynthesis indicated that the early steps of berberine biosynthesis are important in the increased production of berberine.