Apyrase Activity of the Mammary Gland

Abstract

An enzymatic hydrolysis of ATP by prepns. of lactating rat mammary gland was observed. The action was a linear function of time and protein concn. Mg ions depressed apyrase activity of homogenates made with phosphate buffer. In contrast, the addition of Mg to water homogenates produced a stimulation. Fluoride inhibited the apyrase action of either prepn. About 45% of the apyrase was extracted with water. Enzymatic activity of this extract was stimulated by either Ca or Mg ions. The remaining apyrase was associated with cellular debris. Variation in the stimulation with ions suggested the presence of several enzymes.