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Hydrogenation of Unsaturated Fatty Acids by Treponema (Borrelia) Strain B₂5, a Rumen Spirochete¹

^a Department of Dairy Science, Division of Nutrition, University of Illinois, Urbana-Champaign, Illinois 61801

ABSTRACT

The time course of hydrogenation of linoleic acid to trans-11-octadecenoic acid was observed in a growing culture of Treponema (Borrelia) strain B₂5. A conjugated fatty acid, cis-9, trans-11-octadecadienoic acid, was identified as an intermediate in the process. The isomerase responsible for the conversion of linoleic acid to the conjugated fatty acid was found to be associated with a particulate fraction characterized by a high protein and lipid content in a 2:1 ratio. Optimum pH for isomerase activity was found to be 7.0 in 0.05 M potassium phosphate buffer. No cofactor requirements could be demonstrated for the isomerase. The sulfhydryl inhibiting agents, iodoacetamide, N-ethylmaleimide, and p-chloromercuribenzoate, inhibited isomerase activity. Isomerase activity was also inhibited by the metal chelators, o-phenanthroline, , '-bipyridyl, ethylenediaminetetraacetic acid, and 8-hydroxyquinoline. Linoleic (9, 12), linolenic (9, 12, 15), and gamma-linolenic (6, 9, 12) acids served as effective substrates for the isomerase; however, the derivatives of linoleic and linolenic acid did not.

¹ Presented in part at the Federation of American Societies for Experimental Biology Meetings, Atlantic City, N.J., April 1970, and Chicago, Ill., April 1971.