with Parkinson's disease. An adult who consumes a fruit or can of nectar daily over the course of a year is estimated to ingest the same amount of annonacin that induced brain lesions in the rodents receiving purified annonacin intravenously. Biosynthesis Based on basic polyketide synthesis, the biosynthesis of annonacin is likely accomplished by a modular polyketide synthase (PKS). The biosynthesis likely involves the use of 17 modules consisting of a number of enzymes commonly found in PKS. These include the acyl carrier protein (ACP), acetyl transferase (AT), ketosynthase (KS), malonyl transferase (MT; which can come carrying a variety of functionalities), ketoreductase (KR), dehydratase (DH), and enoyl reductase (ER). An example of the possible modular biosynthetic pathway detailing the combination of these enzymes and the subsequent modules can be seen in the figure below. References Furanones Tetrahydrofurans Polyols Polyketides Neurotoxins NADH dehydrogenase inhibitors Respiratory toxins Plant toxins