Palmitoleic acid, hydroxy fatty acids

To improve the separation of the derivatives of fatty acids with the same effective carbon number, e.g., palmitoleic (C16 1), linoleic (18 2), andmyristic (C14 0), Baty et al. (33) reported the preparation of the anthrylmethyl esters derivatives of several fatty acids (with 9-hydroxy-methylanthracene and the catalyst 2-bromo-l-methylpyridinium iodide (BMPI)) with a view to analysis by HPLC and LC-MS (with gradient elution on a ZORBAK 5-/zm Cl8 column) (see Chemical Structure 1). The excess reagents were evaporated under nitrogen at 50°C, and the de-rivatized acids were taken up in 1 ml of mobile phase prior to chromatography. This method did not allow the resolution of the C16 1, 08 2, and C14 0 esters, although HPLC data obtained for the other acids correlated well with that obtained by capillary gas-liquid chromatography. 

Each of the enzymatic activities located in a single polypeptide chain of the mammalian fatty acid synthetase exists as a distinct protein in E. coli. The acyl-carrier protein (ACP) of E. coli has an Mr = 8,847 and contains 4-phosphopantotheine. The dehydratase has a molecular weight of 28,000 and catalyzes either trans 2-3 or cis 3-4 dehydration of the hydroxy acid intermediates in the biosynthesis of palmitic acid. When the chain length of the hydroxy fatty acid is C[ the synthesis of palmitoleic acid is achieved as follows ... 

Based on the postulated common metabolic pathway involved in DOD and TOD formation by PR3, it was assumed that palmitoleic acid containing a singular C9 cis double bond (a common structural property shared by oleic and ricinoleic acids), could be utilized by PR3 to produce hydroxy fatty acid. Bae et al. (2007) reported that palmitoleic acid could be utilized as a substrate for the production of hydroxy fatty acid by PR3. Structural analysis of the major product produced from palmitoleic acid by PR3 confirmed that strain PR3 could introduce two hydroxyl groups on carbon 7 and 9 with shifted migration of 9-cis double bond into 8-tram configuration, resulting in the formation of 7,10-dihydroxy-8( )-hexadecenoic acid (DHD) (Fig. 31.3).The time course study of DHD production showed that DHD formation was time-dependently increased, and peaked at 72 h after the addition of palmitoleic acid as substrate. However, production yield of DHD (23%) from palmitoleic acid was relatively low when compared to that of DOD (70%) from oleic acid (Hou and Bagby, 1991). 

There were limited trials to use palmitoleic acid as substrate for microbial conversion. Flavobacterium sp. DS5 produced 10-keto and 10-hydroxy products from palmitoleic acid (Hou, 1995b) and a filamentous fungus Trichomonas sp. AM076 converted palmitoleic acid to a small amount of 9,12-hexadecadienoic acid (Shirasata et al., 1998). However there was no identified dihydroxy fatty acid product from those microorganisms. 

Various unsaturated fatty acids were efficiently used for the production of various hydroxy fatty acids by bacterial strain P. aeruginosa PR3. Among those unsaturated fatty acids, oleic acid, ricinoleic acid, linoleic acid, palmitoleic acid,... 

The enzyme oleate hydratase (E.C. 4.2.1.53) from Pseudomonas catalyzes the elimination of water from (R)-lO-hydroxystearate or the addition of water to a number of free unsaturated fatty acids, yielding (R)-lO-hydroxy fatty acids. Substrates that have been identified include linoleic acid, oleic acid and palmitoleic acid, which are converted to the corresponding 10-hydroxy-fatty acids 42l... 

The strain DS5 system produced more keto product from palmitoleic and oleic acids and more hydroxy product from myristoleic, linoleic, and a- and y-linolenic acids. The reason for fliis preference is not clear. Among die 18-carbon unsaturated fatty acids, an additional double bond in either side of die C-10 position lowers the enzyme hydration activity. A hterature search revealed diat all microbial hydratases hydrate oleic and linoleic acids at the C-10 position (Fig. 2). Therefore, die positional specificity of microbial hydratases might be universal. 

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