Hentriacontanonaene is a long-chain polyunsaturated hydrocarbon produced by numerous gamma-proteobacteria primarily from the marine environment. Hentriacontanonaene was originally isolated from bacterial isolates from Antarctic sea ice cores.[1] All isolated bacteria that produced hentriacontanonaene also produced the polyunsaturated fatty acidseicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA).[1][2] Given its polyunsaturated nature it has been proposed that this molecule is produced as part of a response to maintain optimal membrane fluidity.[1][3]
Biosynthesis
The biosynthesis of this compound was initially identified by its similarity to other known pathways found in bacteria that produce similar long-chain hydrocarbons.[4] Production of monounsaturated and tri-unsaturated long-chain hydrocarbons in various microbial lineages has been attributed to the oleABCD gene cluster.[3] In this pathway two acyl-CoA or acyl-ACP are condensed using a non-decarboxylative Claisen condensation to yield a β-keto-thioester.[5] Hydrolysis from the enzyme is followed by reduction of the β-keto group to an alcohol catalyzed by an NADPH dependent reductase OleD.[6] The remaining steps include decarboxylation and dehydration, which might be combined as a single decarboxylation elimination step.[6] The exact roles of OleB and OleC in this pathway are unknown, however deletion of oleC yielded a strain that produced a mono-ketone product without the completed olefin.[3]
The overall unsaturation of the compound is determined by the acyl precursors and it has been hypothesized that condensation of two 16:4(n-3) acyl chains by OleABCD yields hentriacontanonaene.[2][3][4] A polyketide-like pathway responsible for the production of eicosapentaenoic acid provides the polyunsaturated precursor for hentriacontanonaene.[3]
