Linoleic acid hydration

Hudson, J.A., Cai, Y., Comer, R.J., Morvan, B., and Joblin, K.N. 2000. Identification and enumeration of oleic acid and linoleic acid hydrating bacteria in the rumen of sheep and cows. J. Appl. Microbiol. 88, 286-292. 

Of interest is a unique alternative biosynthetic pathway for CLA. Ogawa et al. (2001) reported that a strain of Lactobacillus acidophilus, under micro-aerobic conditions, produced 1O-hydroxy-cA-12-octadcccnoic acid and 10-hydroxy-trans-12-octadecenoic acid as intermediates in the synthesis of cis-9, trans-11 and trans-9, cis-11 18 2. The conversion was induced by presence of linoleic acid, and a high yield of CLA was reported. Hudson et al. (1998, 2000) showed that lactic acid bacteria, including Lactobacillus, Pediococcus, and Streptococcus species, are the major unsaturated fatty acid hydrating bacteria in the rumen, converting oleic acid to 10-hydroxy stearic acid and linoleic acid to 10-hydroxy-12-octadecenoic acid and 13-hydroxy-9 octadecenoic acid. Thus, potentially, CLA may be produced also in the rumen from linoleic acid by pathways other than the classic isomerase described by Kepler et al. (1966). 

Oxidation of unsaturated fatty acids requires A -cis-,A -trans-enoyl-CoA isomerase and NADPH-dependent 2,4-dienoyl-CoA reductase, in addition to the enzymes of y3-oxidation. The enoyl-CoA isomerase produces the substrate for the hydration step. The reductase catalyzes the reduction of A -frans-,A -cjs-decadienoyl-CoA to A -rrans-decenoyl-CoA. The latter is isomerized to A -trans-decenoyl isomerase, which is a normal -oxidation intermediate. These reactions are illustrated for oxidation of oleic and linoleic acids in Figures 18-7 and 18-8. 

A Flavobacterium sp. can be used to hydrate linoleic acid to 10-hydroxy-12(2)octadecenoic acid, an analogue of ricinoleic acid.222 Ricinoleic acid (12-hydroxy-9(.Z)oc-tadecenoic acid) from castor oil is important in the preparation of paints and varnishes.223 Cryptococcus neofor-mans can convert /3-pentadecane to the corresponding a-cu-dicarboxylic acid (HOOC(CH2)i3COOH).224 Toluene can be converted to 4-hydroxybenzoic acid... 

Previously, the strain DS5 bioconversion products from oleic and linoleic acids were identified as 10-ketostearic (23) and 10-hydroxy-12(Z)-octadecenoic acid(24), respectively. It is interesting to find that all unsaturated fatty acids tested are hydrated at the 9,10 positions with the oxygen functionality at C-10 despite their varying degree of unsaturations. DS5 hydratase was not active on saturated fatty acids and other non-9(Z)-unsaturated fatty acids such as elaidic [9(.B)-octadecenoic], arachidonic [5( ),8( ),1 l( ),14( )-eicosatetraenoic], and erucic [13( )-docosenoic] acids (25). From all of the data gathered, it is concluded fliat DS5 hydratase is indeed a C-10 positional-specific enzyme. The fact that elaidic acid was not hydrated indicates that die unsaturation must be in flie cis configuration for DS5 hydratase activity. 

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. 

In a patent disclosure, Litchfield and Pierce (13) claimed that cells of Rhodococ-cus rhodochrous catalyzed the hydration of linoleic acid to 10-hydroxy-12-octadecenoic acid at 22% yield with 10-keto-12-octadecenoic acid as a co-product. The hydration enzyme is inducible by the presence of oleic acid at the early stage of cell growth. 

It should be noted that a few hydroxylations occur without a mixed-funtion oxidase enzyme. For example, the ergot fungus Claviceps purpurea forms 12-hydroxyoleic acid (ricinoleic) by hydration of linoleic acid (Harwood and Russell, 1984). 

Linoleic acid A9 hydratase, which is involved in the linoleic acid saturation metabolism of Lactobacillus plantarum AKU 1009a, was cloned as his-tagged recombinant enz une, purified with affinity column, and characterized [30]. The enzyme required FAD as a cofactor for its activity, and the activity was enhanced by NADH. The maximum activities for hydration of linoleic acid and for dehydration of lO-hydroxy-czs-12-octadecenoic acid (HYA) were observed at 37°C, pH5.5, with 0.5M NaCl. C16 and CIS free fatty acids with cis-9 double bond served as substrates for hydration with CIO regiospecificity and (S) stereospecificity (Figure 22.9). 10-Hydroxy fatty acids served as substrates for dehydration reactions. The apparent value for linoleic acid was estimated to be 92 irM with its values at 2.6 x 10 s and Hill factor was 3.3. The apparent K value for HYA was estimated to be 98 iM with its values at 1.2 x 10 s ... 

Substrate specificity of hydration reaction catalyzed by linoleic acid A9 hydratase. 

Cowan Teeter (1944) reported a new class of resinous substances based on the zinc salts of dimerized unsaturated fatty acids such as linoleic and oleic acid. The latter is referred to as dimer acid. Later, Pellico (1974) described a dental composition based on the reaction between zinc oxide and either dimer or trimer acid. In an attempt to formulate calcium hydroxide cements which would be hydrolytically stable, Wilson et al. (1981) examined cement formation between calciimi hydroxide and dimer acid. They found it necessary to incorporate an accelerator, alimiiniiun acetate hydrate, Al2(OH)2(CHgCOO)4.3H2O, into the cement powder. 

It has been reported that a microbial isolate, Flavobacterium sp. strain DS5, produced 10-ketostearic acid (10-KSA) from oleic acid in 85% yield (Hou, 1994a). The purified product was white, plate-like crystals melting at 79.2°C. A small amount of 10-hydroxystearic acid (10-HSA) was also produced during the bioconversion, suggesting that oleic acid is converted to 10-KSA via 10-HSA, and the enzyme catalyzing the hydration is C-10 positional specific (Hou, 1994b, 1995). The DS5 bioconversion products from oleic, linoleic, a-linolenic, and y-linolenic acid are all 10-hydroxy fatty acids. The optimum time, pH, and temperature for the production of 10-KSA have been reported in flask... 

Reaction of linoleate with toluene-4-sulfonic acid could conceivably be a method of hydrating one or both of the double bonds. In fact, the major products were the 9,12-and lOjlS-tetrahydrofiuans (44%) accompanied by the 9,13-tetrahydropyran (4%) and smaller amounts of isomeric tetrahydrofiuans (8,11-, 10,13-, and 11,14-) and tetrahydropyrans (8,12- and 10,14-) (Scheme 7). These compounds were readily identified by a combination of chromatographic and spectroscopic techniques (10). Similar products were obtained with the trans isomers of linoleate (but not with the conjugated 9,11- and 10,12-dienoates) and from several oxygenated monoene esters... 

More recently, Koritala and Bagby (28), using washed resting cells suspension of Nocardia cholestewlicum under anaerobic conditions, reported the hydration of linoleic and linolenic acids to 10-hydroxy-12(Z)-octadecenoic (5ueld 71%) and 10-hydroxy-12(Z),15(Z)-octadecadienoic acids (yield 77%), respectively. The production of 10-hydroxy fatty acids by hydratase from various microbes is summarized in Table 1. 

This enzyme oxidizes linoleic and linolenic acids rapidly in whole flour or milling products containing wheat germ or bran mixed with water. The initial hydroperoxides formed by lipoxygenases in stored wheat bran are converted to secondary products, mono- and trihydroxy fatty acids. These oxidation products causing bitter and rancid flavors are formed in higher concentrations in hydrated products than in dry raw materials. Rancid flavors develop rapidly on hydration. 

Some substances, usually included in moisturizers, have other potential beneficial effects on dry skin (1) the L-isomer of lactic acid increases the endogenous synthesis of ceramides and promotes the incorporation of linoleate, instead of oleate, into ceramide 1 (Rawlings et al. 1996) (2) glycerol and other polyols prevent lipid crystallinity (Rawlings et al. 1994), increase SC humidity and promote corneosome digestion and, consequently, the unicellular invisible desquamation (Rawlings et al. 1995) (3) alpha-hydroxy acids improve keratinization and SC hydration (Leyden et al. 1995) and (4) silicones or silicone-based barrier creams may have an extra protective effect on external aggressions. 

Hydration.—Pseudomonas species of bacteria effect the stereospedfic hydration of unsaturated acids, acting on the following substrate acids to give, in 20—40% yield, the product indicated in parentheses oleic (lOo-hydroxy-stearic acid), linoleic (10D-hydroxyoctadec-c -12-enoic acid), linolenic... 

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