Brazzein a small, sweet protein: discovery and physiological overview.

For many years, only small molecules were considered capable of inducing a sweet taste (cf. Inglett, 1974). This idea was shattered when miraculin from the miracle fruit of Synsepalum dulcificum was shown to have (Brouwer et al., 1968; Kurihara and Beidler, 1968) a mol. wt of 24 600. The search for sweeteners was no longer limited to small molecules and resulted within a few years in the discovery of monellin and thaumatin (Morris and Cagan, 1972; van der Wel and Loeve, 1972). Later, mabinlin and curculin were discovered (Hu and He, 1983; Yamashita et al., 1995). In the 1980s, our attention was attracted to a West African plant, Pentadiplandra brazzeana (Hladik et al., 1984). We obtained a small sample of smoke-dried berries in which we tentatively identified a sweet tasting protein, pentadin (van der Wel et al., 1989). From a new and fresher sample of the berries’ pulp we identified and isolated the major sweet principle of P. brazzeana, which we named brazzein (Ming and Hellekant, 1994). Brazzein is distributed in the pulp between the epicarp the seeds and turns from green to red during ripening (Figure 1a). The content of brazzein in the ripe fruit appears to be roughly 0.2–0.05% by weight.