Accumulation of ixerin F and activities of some terpenoid bisynthetic enzymes in a cell suspension culture of Lactuca virosa L.

A cell suspension culture of <em>Lactuca virosa</em> L. (<em>Asteraceae</em>, tribe <em>Lactuceae</em>) is capable of synthesizing sesquiterpene lactones of which ixerin F is the main compound. The culture was characterized on growth (by dissimilation rates), on ixerin F accumulation (by RP-HPLC) and on some enzyme activities involved in early steps of terpenoid biosynthesis. Acetoacetyl-coenzyme A thiolase (AACT, E.C. 2.3.1.9) and 3S-hydroxy-3-methylglutaryl-coenzyme A synthase (HMGS, E.C. 4.13.5) activities of the cells were assayed spectrophotometrically. HMGS activity increased during the culture period and reached a maximum during the stationary phase (190 pkat/mg protein), while AACT showed relatively high level of activity throughout the growth cycle, with transient decrease at the logarithmic growth phase and the beginning of stationary phase. Ixerin F accumulated inside the cells and the maximum concentration of 0.08% (on dry weight basis) was found in the early stationary phase of the growth cycle of the culture.