Fatty acyl-CoA reductases of birds

Abstract

BackgroundBirds clean and lubricate their feathers with waxes that are produced in the uropygial gland, a holocrine gland located on their back above the tail. The type and the composition of the secreted wax esters are dependent on the bird species, for instance the wax ester secretion of goose contains branched-chain fatty acids and unbranched fatty alcohols, whereas that of barn owl contains fatty acids and alcohols both of which are branched. Alcohol-forming fatty acyl-CoA reductases (FAR) catalyze the reduction of activated acyl groups to fatty alcohols that can be esterified with acyl-CoA thioesters forming wax esters.ResultscDNA sequences encoding fatty acyl-CoA reductases were cloned from the uropygial glands of barn owl (Tyto alba), domestic chicken (Gallus gallus domesticus) and domestic goose (Anser anser domesticus). Heterologous expression in Saccharomyces cerevisiae showed that they encode membrane associated enzymes which catalyze a NADPH dependent reduction of acyl-CoA thioesters to fatty alcohols. By feeding studies of transgenic yeast cultures and in vitro enzyme assays with membrane fractions of transgenic yeast cells two groups of isozymes with different properties were identified, termed FAR1 and FAR2. The FAR1 group mainly synthesized 1-hexadecanol and accepted substrates in the range between 14 and 18 carbon atoms, whereas the FAR2 group preferred stearoyl-CoA and accepted substrates between 16 and 20 carbon atoms. Expression studies with tissues of domestic chicken indicated that FAR transcripts were not restricted to the uropygial gland.ConclusionThe data of our study suggest that the identified and characterized avian FAR isozymes, FAR1 and FAR2, can be involved in wax ester biosynthesis and in other pathways like ether lipid synthesis.

Biotechnological potential of insect fatty acid-modifying enzymes

“…+ binding domain and the C-terminal FAR_C domain is conserved among the FARs [89,96,98,100]. The common dehydrogenase/reductase active site motif YXXXK was experimentally confirmed to be indispensable for FAR enzymatic activity [167].…”

“…Heterologous expression of plant FARs in Escherichia coli, rapeseed (B. napus), and Saccharomyces cerevisiae led to a range of saturated and unsaturated alcohols of C14 to C26 chain length, depending on the host organism [100,114,115]. Besides plant FARs, microbial FAR genes [102,116,117] and FARs from vertebrates have also been isolated and functionally described [97,98].…”

“…The fatty alcohols are precursors of waxes that serve as surface-protective compounds in plant pollen [96], preventing excessive water loss in insects [29], and are secreted as skin-, eye-, or featherprotective compounds in mammals and birds [97,98]. The fatty alcohols are also components of ether lipids, which are abundant in the cell membranes of cardiac, nervous and lymphoid tissues [99].…”

Wax Esters: Chemistry and Biosynthesis

“…Since then fatty acid acyl-CoA reductases have been found and purified from bacteria, plants, and animals, including sebaceous glands (Hellenbrand et al 2011;Cheng and Russell 2004a;Moto et al 2003;Honsho et al 2010). Microsomes from bovine meibomian gland and avian uropygial glands also catalyze reduction of fatty acyl-CoA to alcohol without release of any aldehyde intermediates (Kolattukudy and Rogers 1986).…”

Identification of Amino Acids Conferring Chain Length Substrate Specificities on Fatty Alcohol-forming Reductases FAR5 and FAR8 from Arabidopsis thaliana

“…Primary fatty alcohols and their derivatives have a wide range of biological roles in bacteria, fungi, insects, plants, and animals. Some important functions of free and esterified fatty alcohols in nonplant organisms are as follows: 1) as an energy storage reserve in microorganisms such as Euglena gracilis, Acinetobacter sp., and some marine microalgae; 2) as a constituent of sex pheromones in some insect and reptile species; 3) as a uropygial gland secretion in birds to maintain feather condition; 4) in the heads of sperm whales for echolocation and possibly to regulate buoyancy; and 5) as ether lipids, which play a variety of roles and are highly abundant in animal nervous system tissue (2)(3)(4)(5)(6)(7)(8)(9)(10). In plants, fatty alcohols and their derivatives are found primarily as chemical constituents of three extracellular lipid-phenolic barriers as follows: cuticle coating the aerial surfaces of plants, suberin present in the cell walls of various external and internal tissue layers, and sporopollenin found in the outermost layer of the pollen spore coat (1,11).…”