Construction of novel fatty acid ester library and its application

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The aim of this study was to construct a library consisted of novel fatty acyl esters of various sterols such as cholesterol and phytosterols. To esterify sterols with fatty acids, we used a cholesterol esterase, which we found in this study in culture filtrate of the Streptomyces sp. X9. The enzyme was purified and its gene was cloned, and revealed to constitute a novel family of esterases distributed in actinobacteria. We also constructed an efficient bioconversion system based on recombinant Escherichia coli system producing the fungal cytochrome P450foxy (P450foxy) that hydroxylates subterminal carbons of fatty acids. This system will provide variety of hydroxyl fatty acids to be esterified with sterols. During course of studies on P450foxy, we revealed that it hydroxylated aliphatic alcohols to produce alkyl diols as well although reaction rates were lower than for fatty acids. Another objective of this study was to reveal physiological and physical properties of unique carotenoid compounds of the thermophilic Thermus thermophilus. Major results were as follows. (1) Characterization of bacterial beta-carotene 3, 3'-hydroxylases, CrtZ, and P450 in astaxanthin biosynthetic pathway and adonirubin production by gene combination in Escherichia coli and (2) finding of stabilizing effect of liposomal membranes by carotenoids such as zeaxanthin, zeaxanthin glucoside and thermozeaxanthin both of which are specific products of T. thermophilus. Finally, we succeeded in synthesizing various sterol esters of fatty acids by the actinobacterial cholesterol esterase. The produced esters were those combined with palmitic, myristic, linoleic, and stearic acids as fatty acyl moieties and cholesterol, ergosterol, and stigmasterol as sterol moieties. Lanosterol was inactive in our system.