Platelet‐activating factor detection, metabolism, and inhibitors in the ethanologenic bacterium Zymomonas mobilis

Platelet-activating factor (PAF) is a signaling phospholipid with a significant physiological role in multicellular and unicellular organisms, including fermentative organisms such as yeast. Zymomonas mobilis is an ethanologenic α-proteobacterium currently studied for bioethanol production. In order to examine the presence of PAF and/or PAF inhibitors in Z. mobilis, a new one-step high performance liquid chromatography (HPLC) separation procedure of total lipids was performed, using a C8 reversed-phase semi-preparative column. According to this method and to bioassays based on washed rabbit platelet aggregation, two lipid molecules with PAF-like activity and same retention times as those of standard PAF were detected; electron-spray ionization MS and MS/MS analysis revealed that they share similar structure with 16:0 and 18:0 PAF. Furthermore, other lipids extracted from Z. mobilis were found to exhibit a potent anti-PAF activity. Enzyme activities indicative of key PAF biosynthetic enzymes, such as dithiothreitol-insensitive cholinephosphotransferase (PAF-CPT) and lyso-PAF acetyltransferase were detected in Z. mobilis homogenates. As for PAF degradation, activity similar to that of PAF acetylhydrolase was also discovered. Overall, the presence of PAF, PAF-specific inhibitors, and enzyme activities relating to PAF metabolism, suggests that PAF may play an intrinsic role in this biotechnological organism. Practical applications:Z. mobilis is a platform microorganism for bioethanol production and a potential source of high-value chemicals of interest to the food and healthcare industries. Further investigation of PAF's role is bound to affect applications involving this and other biotechnological organisms. The finding that Z. mobilis lipids exhibit potent anti-PAF activity opens up prospects for their identification, overproduction and pharmaceutical use. The presented HPLC method for lipid fractionation accomplishes a one-step separation of lipids from dense samples, which may be successfully employed to other lipid-rich sources such as blood.