178. A lipase (tributyrinase) of cows' milk. I. Occurrence, method of estimation and relationship to lactation cycle

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Abstract
An enzyme which hydrolyses tributyrin is present in all samples of fresh cows' milk examined. A method has been developed for the determination of the tributyrinase activity of a given milk or fluid.In milk the enzyme is present in the aqueous rather than the fatty portion. Its optimal range of activity is in the regionpH 8·2–8·7. It is rather more thermolabile than phosphatase.Its concentration in milk varies considerably from cow to cow, and in individual healthy cows there is a fairly regular variation throughout the lactation cycle. It is highest in concentration in colostrum, then the concentration falls to a minimum at about 10 days, rising later to a figure intermediate between this minimum and the colostral value. It shows no sign of increase towards the end of the lactation period.Its relationship to the “true lipase” of milk is discussed.