Biosynthesis of Natural Products

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Science  17 May 1974:
Vol. 184, Issue 4138, pp. 760-764
DOI: 10.1126/science.184.4138.760


The experimental verification of a proposed biosynthetic pathway for a given natural product is often difficult to obtain with the use of the whole organism (permeability factors) or, in the case of higher plants, a cell-free system. Until the purified enzyme for each step of biosynthesis is available, biosynthetic studies can, however, be carried out, albeit with modest incorporation values, by means of either hydroponic or injection methodology. Where viable seed sources are available it is suggested that improvements of several orders of magnitude in incorporation can be achieved by a short-term incubation (small pool size of precursors; trapping of reactive intermediates) or a long-term feeding (equilibration of precursor with the compartmentalized or induced synthetases). In bacterial, fungal, mammalian, and plant systems, where incorporation efficiencies provide the opportunity to study 13C enrichment (at least equal to natural abundance of the isotope), we can expect a rapid expansion since the method removes the tedium of carbon-by-carbon degradation. For the next few years, however, the prognosis would seem to favor parallel studies of 13C and 2H, and of 14C/3H ratio techniques since the last-mentioned method provides more information concerning the stereoselectivity of labeling processes on the microgram scale.