Unsaturated fatty acids are the active molecules of a glucan-synthase-inhibitory fraction isolated from entomophthoralean protoplasts.

A few entomophthoralean species are able to multiply in a protoplast form. The polysaccharide synthases which synthesize the cell wall are inactivated in this form. An inhibitor of one of the key enzymes of wall synthesis, glucan synthase, was isolated from entomophthoralean protoplasts, using silica column chromatography and HPLC. Thin-layer and gas chromatography revealed free fatty acids in the inhibitory fractions. These fatty acids, including long-chain unsaturated fatty acids, were shown to be responsible for the inhibition of glucan synthase. The fatty acids were generated during incubation of a protoplast homogenate for 36 h at 37 degrees C and were shown to be non-competitive and non-specific inhibitors of glucan synthase.