Biosynthetic pathway of aliphatic formates via a Baeyer-Villiger oxidation in mechanism present in astigmatid mites

Abstract

Astigmatid mites depend on bioactive glandular secretions, pheromones, and defensive agents to mediate intra- and interspecies interactions. Aliphatic formates, such as (Z,Z)-8,11-heptadecadienyl formate (8,11-F17) and (Z)-8-heptadecenyl formate (8-F17), are rarely encountered natural products that are abundant in Sancassania sp. Sasagawa (Acari: Acaridae) mite secretions. Linoleic acid and oleic acid are predicted as key intermediates in the synthesis of the closely related aliphatic formates. To gain insight in this biosynthetic pathway, acarid mite feeding experiments were conducted using 13C-labeled precursors to precisely track incorporation. Analyses using 13C NMR spectroscopy demonstrated that the 13C-labeling pattern of the precursors was detectable on formates in exocrine secretions and likewise on fatty acids in total lipid pools. Curiously, the results demonstrated that the formates were biosynthesized without the dehomologation of corresponding fatty acids. Careful examination of the mass spectra from labeling experiments revealed that the carbonyl carbon of the formates is originally derived from the C-1 position of the fatty acids. Consistent with a Baeyer-Villiger oxidation reaction, labeling studies support the insertion of an oxygen atom between the carbonyl group and carbon chain. Empirical data support the existence of a Baeyer-Villiger monooxygenase responsible for the catalyzation of the Baeyer-Villiger oxidation. The predicted existence of a Baeyer-Villiger monooxygenase capable of converting aliphatic aldehydes to formates represents an exciting opportunity to expand the enzymatic toolbox available for controlled biochemical synthesis.