Modification of bactericidal fatty acids by an enzyme of Staphylococcus aureus

Certain strains of Staphylococcus aureus produce an enzyme capable of inactivating the bactericidal fatty acids produced in staphylococcal abscesses by esterification to various alcohols. The enzyme, called FAME (fatty acid modifying enzyme), has a pH optimum between 5.5 and 6.0 and a temperature optimum of about 40 degrees C. Enzyme activity is not affected by edetic acid or by the presence or absence of sodium and potassium ions. Although FAME can utilise methanol, ethanol, 1-propanol, 2-propanol, 1-butanol or cholesterol as substrates, cholesterol appears to be the preferred substrate. FAME esterifies without being an esterase operating in reverse. Strains capable of producing the enzyme can synthesise it in trypticase soy broth and in a chemically defined medium, but not necessarily in equal amounts. FAME production is correlated with the ability of a strain to grow and survive within the tissues.