FIGURE 2.

Schematic biosynthetic pathway of the antimalarial compound FR900098 in S. ruberllomurinus and S. roseosporus. The pyridoxal phosphate-dependent decarboxylase/aminotransferase reaction is performed by FrbH, an enzyme that is modified by acetylation at three different lysine residues. The reaction activates 2-amino-4-phosphonobutyrate with CTP and decarboxylate this compound forming 5′-CMP-3-aminopropylphosphonate. All the subsequent intermediates appear to be activated with CMP that is released at the final step of the pathway to give FR900098 (see text for details).