Studies on human polymorphonuclear leukocyte enzymes. II. Comparative study of the physical properties of primary and specific granules

Abstract

1. 1. Seven distinct acid hydrolase activities present in cytoplasmic extracts from human polymorphonuclear leukocytes occur in latent form to the extent of 14–30% of their total activity, depending on the enzyme. This latency can be decreased or suppressed by exposure to Triton X-100 or to media of low osmotic pressure, by treatment in a Waring blender, by very acid pH and by freezing and thawing, but not by increasing the substrate concentration in the assay medium up to 16-fold the Michaelis constant of the enzymes. In preparations subjected to graded activating treatments, acid hydrolases are released in closely parallel fashion, suggesting that they are associated with particles possessing similar properties 2. 2. Acid phenylphosphatase and cyanide-insensitive NADH oxidase exhibited no latency under the conditions of the present experiments. It is concluded that, with the exception of acid phenylphosphatase activity, the acid hydrolases studied are associated with lysosome-like particles 3. 3. Alkaline phosphatase (EC 3.1.3.1) is also partly (44%) latent in cytoplasmic extracts of human polymorphonuclear leukocytes. Latent alkaline phosphatase can be released by some of the treatments that suppress the latency of the lysosomal enzymes, but differs from the latter by a complete insensitivity to exposure to media of low osmotic pressure and by an absolute requirement of an ionic media in order to maintain its latency. It is concluded from these results that the alkaline phosphatase-containing granules have some physical properties different from lysosomes.