Characterization of a novel unsaturated fatty acid hydratase from Lactobacillus acidophilus useful for the production of hydroxy fatty acid

We have previously studied how dietary fatty acids are metabolized by gut microbiota and demonstrated that Lactobacillus plantarum can saturate linoleic acid using enzymes such as hydratase (CLA-HY), dehydrogenase (CLA-DH), isomerase (CLA-DC), and enone-reductase (CLA-ER). Additionally, we identified metabolic intermediates, including hydroxy fatty acids (hydration products), oxo fatty acids, and conjugated fatty acids in the unsaturated fatty acid saturation process. Some of these intermediates have been found to show physiological effects.

In this study, we screened gut microbiota for metabolizing linoleic acid and revealed that Lactobacillus acidophilus NTV 001 converted linoleic acid into 13-hydroxy-9(Z)-octadecenoic acid. We investigated the genome information of L. acidophilus strains and found two genes with protein sequences homologous to that of CLA-HY in L. acidophilus ATCC 4796. We amplified the candidate genes using L. acidophilus NTV 001 genomic DNA as a template and transformed them into E. coli.

Product analysis of the reaction mixtures, using E. coli cells expressing each gene and linoleic acid as the catalyst and substrate respectively, revealed that one gene product generated 10-hydroxy-12(Z)-octadecenoic acid, a Δ9-hydration product, while the other gene product, named FA-HY, generated 13-hydroxy-9(Z)-octadecenoic acid, a Δ12-hydration product.

Through substrate specificity analysis, we found that FA-HY could convert free fatty acids such as linoleic acid, α-linolenic acid, γ-linolenic acid, and stearidonic acid into their corresponding 13-hydroxy fatty acids via Δ12-hydration. Furthermore FA-HY was also able to covert C20 unsaturated fatty acid, arachidonic acid, into 14-hydroxy-4(Z),7(Z),10(Z),16(Z)-docosatetraenoic acid.