Heneicosapentaenoic acid

Heneicosapentaenoic Acid (HPA) is a 21:5 omega-3 fatty acid found in trace amounts in the green alga B. pennata and in fish oils. Its chemical composition is similar to eicosapentaenoic acid (EPA), except that a carbon is extended at the carboxy terminus, placing the first double bond at the δ6 position. HPA can be used to study the importance of double bond position in omega-3 fatty acids. It incorporates phospholipids and triacylglycerols in vivo with the same efficiency as EPA and docosahexaenoic acid, and exhibits a strong inhibitory effect on the synthesis of arachidonic acid from linoleic acid. HPA is a poor substrate for prostaglandin H synthase (PGHS) (cyclooxygenase) and 5-lipoxygenase, but retains the ability to rapidly inactivate PGHS.