Anaerobic lipoxygenase activity from Chlorella pyrenoidosa

The micro-alga Chlorella pyrenoidosa expresses an enzymatic activity that c leaves the 13-hydroperoxide derivatives of linoleic acid [13-hydroperoxy-9( Z), 11(E)-octadecadienoic acid, 13-HPOD] and linolenic acid [13-hydro perox y-9(Z),11(Z),15(Z)-octadecatrienoic acid, 13-HPOT] into volatile C-5 and no n-volatile C-13 ore-products. This enzymic activity initially was attribute d to a hydroperoxide lyase enzyme; however, subsequent studies showed that this cleavage activity is the result of lipoxygenase activity under anaerob ic conditions, Headspace analysis of the volatile products by GC/MS showed the formation of pentane when the substrate was 13-HPOD, whereas a more com plex mixture of hydrocarbons was formed when 13-HPOT was the substrate. Ana lysis of the non-volatile cleavage products from 13-HPOD by liquid chromato graphy/MS indicated the formation of 13-oxo-9(Z),11(E)-tridecadienoic acid (13-OTA) along with the 13-keto-octadecadienoic acid derivative. When the s ubstrate is 13-HPOT, liquid chromatography/MS analysis indicated the format ion of 13-OTA as the major non-volatile product. Aldehyde dehydrogenase (Al dDH) oxidizes 13-OTA to an omega -dicarboxylic acid, whereas alcohol dehydr ogenase (ADH) reduces 13-OTA to an omega -hydroxy carboxylic acid. AldDH an d ADH require the oxidized (NAD(+)) and reduced (NADH) forms of the cofacto r NAD, respectively. By combining the action of AldDH and ADH into a contin uous cofactor-recycling process, it is possible to simultaneously convert 1 3-OTA to the corresponding omega -dicarboxylic acid and omega -hydroxy carb oxylic acid derivatives.