THE EFFECT OF OLEIC ACID AND OF BIOTIN ON THE FORMIC HYDROGENLYASE AND FORMIC DEHYDROGENASE ENZYME SYSTEMS

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Abstract
Employing a biotinless mutant strain of Escherichia coli, as well as several wild strains of this organism, it was found that cells harvested from a synthetic medium containing biotin (10-3 [mu]g./ml.) exhibited a lower rate of glucose, pyruvate, and formate fermentation than similar cells harvested from the medium containing oleate (10-100 [mu]g./ml.) in place of biotin. The formic hydrogenylase and formic dehydrogenase enzyme systems were chosen for further study, and it was found that the presence of oleate in the growth medium was necessary for optimal activity. The addition of oleate (10-100 [mu]g.) to washed suspensions of biotin-grown cells resulted in immediate stimulation of formic hydrogenlyase activity, suggesting that oleate or some substance readily synthesized from it by the cells functions as a cofactor in this system. Biotin in some manner antagonizes the oleate effect. This was ascertained in 2 ways. First, the activity of cells harvested from a medium containing both oleate and biotin is about half that found in cells grown only with oleate, and 2d. cells harvested from a medium containing biotin in excess of 10-4-10-3 [mu]g./ml. cannot be stimulated by the addition of oleate. The results of these studies represent perhaps the 1st metabolic role of a fatty acid.