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Some Esterases of Cows' Milk¹

Department of Dairy Science, State University of Washington, Pullman

ABSTRACT

The influence of different concentrations of the organophosphorous enzyme inhibitors, N,N'-diisopropyl phosphorodiamidofluoridate, diethyl p-nitrophenyl thiophosphate, diisopropyl fluorophosphate, and tetraethyl pyrophosphate on the activity of milk enzymes toward phenyl acetate, phenyl propionate, tributyrin, benzyl butyrate, and the butyryl and stearoyl esters of 2-naphthol-6-SO₃Na was studied, using Warburg manometric techniques at pH 8.0 and 37° C. Raw mixed milk served as the enzyme source.

Three distinct esterases or esterase systems were evident. One was responsible for about 95% of the activity of the milk enzymes toward tributyrin, benzyl butyrate, and the butyryl and stearoyl esters of 2-naphthol-6-SO₃Na, the second for 60 to 70% of their activity toward phenyl propionate, and the third for about 80% of their activity toward phenyl acetate. Each of these esterases appeared to hydrolyze one or more of the other substrates. A probable classification of these enzymes is outlined.

¹ Scientific Paper No. 1855.