The effect of fatty acid chain length on the rate of arylester hydrolysis by various albumins.

A series of synthetic chromogenic and fluorogenic substrates for monitoring the arylesterase-like activity of albumins from various sources has been studied. Except for ovalbumin, all displayed enzyme-like activity. The acetate, butyrate, caprylate, laurate, and palmitate esters of a coumarin dye were found to be efficiently hydrolyzed within the pH range 8.8-9.8, with the non-enzymatic rate being highest for acetate and lowest for laurate. The latter is considered to be the substrate of choice because it is cleaved most quickly by the proteins tested. A considerable increase in hydrolytic activity was observed upon addition of detergents, but not of Ca and Mg ions, while addition of 1 equivalent of lauric acid to BSA resulted in a 30% decrease in its activity. The results are interpreted in terms of the well-known affinity of albumins for long chain fatty acids and provide the basis for a sensitive determination of small amounts of albumins.