CHOLESTEROL ESTERASE ACTIVITY OF PLEUROPNEUMONIALIKE ORGANISMS

Abstract

Cholesterol esterase activity toward cholesteryl esters of several short and long-chained fatty acids was demonstrated to be present in pleuropneumonialike organisms. Lipase activity was also found but was demonstrated to be distinct from the cholesterol esterase activity. Those strains requiring a lipoprotein growth factor possess considerably greater esterase activity than strains not requiring the growth factor, although lipase activities among strains were equivalent. Hydrolysis of an ester results in equimolar formation of free cholesterol and fatty acid. Cholesterol was not further degraded. The fatty acid can appear as acyl coenzyme A under appropriate conditions. Optimum pH for hydrolysis is 6.5 and synthesis, pH 6.2. No absolute cofactor requirement for hydrolysis was noted but surface active compounds and coenzyme A were stimulatory. Coenzyme A, adenosinetriphosphate and taurocholate were required for synthesis. The major portion of the activity is associated with the cellular debris after sonic lysis. The reaction appears to be specific for fatty acid esters of 3B-hydroxy A 5 sterols. Inhibition of the hydrolysis reaction was noted with growth inhibitory sterols and other compounds. The possible role of the cholesterol together with the lipoprotein requirement in cellular function is discussed. The data presented appears to favor some function relative to substrate permeability.